Journal of Molecular Liquids (18733166)393
This study comprehensively investigates the effects of hydroxyl groups in side chains and cation symmetry on intra- and inter-molecular structures, dynamics, and thermodynamic properties of two hydroxyl-functionalized di-cationic ionic liquids (HFDILs). Using a combination of molecular dynamics (MD) simulations and quantum chemistry (QC) calculations, we compare the influence of these effects on various properties with corresponding non-hydroxyl DILs reported in previous works. The structure of HFDILs is explored using angle distribution, radial distribution, spatial distribution, and combined distribution functions. Also, the averaged noncovalent interaction (aNCI) analysis is used to characterize the weak noncovalent interactions in fluctuating environment of HFDILs. Results showed that the oxygen atoms of anion have the strongest interaction with the hydrogen atom of hydroxyl group, followed by the hydrogen atom at the top of the imidazolium ring. Domain analysis and Voronoi calculations are performed to investigate the number of polar and non-polar subunits, revealing that symmetric HFDILs with two hydroxyl groups in their side chains have greater structural heterogeneity than asymmetric ones with only one hydroxyl group due to the larger accumulation of non-polar subunits. To investigate dynamical heterogeneity, we calculate the non-Gaussian parameter, van Hove correlation, hydrogen bond, ion pair, ion cage, and reorientation dynamics. Results indicated that symmetric HFDILs have slower dynamics, greater dynamic heterogeneity, and more stability than asymmetric ones. Finally, the structure and strength of ion triplet interactions are examined using quantum mechanical methods, revealing that symmetric HFDILs are more stable than asymmetric ones. This study provides valuable information for understanding DILs and their potential applications in various fields. © 2023 Elsevier B.V.
Journal of Chemical Physics (10897690)159(24)
In this study, we extended the optimized potentials for liquid simulation-ionic-liquid virtual site (OPLS-VSIL) force field (FF) to imidazolium-based dicationic ionic liquids (DILs) and evaluated the ability of different OPLS-based FFs (i.e., OPLS-2009IL, 0.8*OPLS-2009IL, and OPLS-VSIL) in predicting different properties of the studied DIL by comparing their results with ab initio molecular dynamics (AIMD) simulation and experimental results. To achieve this purpose, MD simulations with three different OPLS-based FFs as well as AIMD simulation were performed for [C3(mim)2][NTF2]2 DIL and its structural, dynamical, vibrational, and volumetric properties were analyzed. Structural properties of the studied DIL, i.e., radial distribution functions (RDFs), structure factor, and hydrogen-bond network, showed that compared to 0.8*OPLS-2009IL FF, there is a much better agreement between the results of both OPLS-2009IL and OPLS-VSIL FFs with the AIMD simulation. On the other hand, the results of dynamical properties, such as mean square displacements, van Hove correlation functions as well as hydrogen bond, ion pair, and ion cage dynamics, depicted that in both 0.8*OPLS-2009IL and OPLS-VSIL FFs, the dynamics of the system is almost similar, and compared to OPLS-2009IL FF, they have better agreements with experimental results where they exist. So, it can be seen that although reducing the total charge of studied DIL by 20% leads to an increase in the dynamics of the system, the type distribution of partial charges on each atom does not significantly affect the system’s dynamics. The calculated infrared (IR) and power spectra showed that the vibrational features of studied DIL in three OPLS-based FFs are mostly the same and reducing total charge and different type distribution of partial charges have no significant effect on the studied system. Furthermore, in volumetric properties, OPLS-VSIL FF shows somehow better agreement with experimental results. Overall, the evaluation of different structural, dynamical, vibrational, and volumetric properties of [C3(mim)2][NTF2]2 DIL shows that the OPLS-VSIL FF may be the best choice among the different studied OPLS FFs. © 2023 Author(s).
Journal of Chemical Physics (10897690)158(2)
Dicationic ionic liquids (DILs) have been shown to be useful as an effective solvent for the absorption of CO2. However, compared to monocationic ionic liquids (MILs), they have been less investigated for this application. Previous studies on MIL-CO2 systems have shown that anions play the main role in tuning CO2 capture, but the partial negative charge on the oxygens of CO2 may interact with cation centers and, especially, for DILs with two charge centers, the role of cations can be significant. Therefore, the current work focuses on how cation symmetry and the length of side chains affect interactions and also the dynamical and structural properties of DIL-CO2 systems using molecular dynamics simulation. In addition, the effect of CO2 on the infrared vibrational spectra of isolated ions and ion triplet (DIL molecules) was studied using density functional theory calculations and the observed red and blue shifts have been interpreted. The results indicated that symmetric cation with longer side chains tend to interact more strongly with CO2 molecules. It seems that increasing the length of the side chains causes more bending of the middle chain, and in addition to increasing the free fraction volume, it weakens the interaction between cations and anions, and as a result more interaction between gas and cation. The results of this work may contribute to the rational molecular design of DILs for CO2 capture, DIL-based gas sensors, etc. © 2023 Author(s).
Journal of Molecular Liquids (18733166)382
MXenes alongside ionic liquid electrolytes have been promising in energy storage systems. The nanoscopic structure of two biodegradable choline-based ionic liquids (CBILs) and their water mixtures were investigated near the MXene surface using quantum mechanics calculations and molecular dynamics simulations. Quantum mechanics calculations showed that the anion-cation interactions in the choline salicylate ([CH][SA]) are weaker than that for choline β-alaninate ([CH][β-Ala]), therefore, [SA]− tends to interact more with the MXene surface compared to [β-Ala]−. Simulation results indicated that the ionic liquids aggregate in the vicinity of the MXene surface to form a dense layer with significantly different properties compared to bulk. Applying moisture to CBIL systems reduces the ion population in the first layer and also their structural correlations. Furthermore, there is a competition between water molecules and choline cations for interaction with anions. The presence of water molecules also increases the dynamics of hydrogen bonds, ion pairs, and ion cages. Perception of the nano-scale behavior of these unique classes of ionic liquids on MXenes could be beneficial for energy storage systems like batteries and electric double-layer capacitors. © 2023 Elsevier B.V.
Colloids and Surfaces A: Physicochemical and Engineering Aspects (18734359)674
This study explores the potential of using biodegradable choline-based ionic liquids (CBILs) as a more sustainable and eco-friendly alternative to classical ILs in the field of electrolyte media for energy storage devices. While previous studies have focused on electrostatic and capacitance properties, it is important to also consider dynamics and structural behavior when choosing adjustable electrolytes and electrodes. In this regard, molecular dynamics simulations were used to study the structural, spectral, and dynamical behaviors of two CBILs ([Ch][Sa] and [Ch][β-Ala]) inside MXene nanopores with varying pore size and surface charge density. As the pore size decreases, the number of hydrogen bonds in the first layer decreases from 0.447 to 0.122 and 0.154–0.063 in [Ch][Sa] and [Ch][β-Ala], respectively. Also, the presence of an aromatic ring benefits packing efficiency, causing [Sa]- to have a parallel orientation relative to MXene surface. Applying a fixed charge (1.8–7.2 μC/cm2) on MXene electrodes results in the formation of an electric double layer (EDL). At higher surface charge densities, there is slower dynamics and lower structural correlations between anions and cations. Moreover, Infrared (IR) spectra show blue and red shifts for the O-H bond in choline and carbonyl C-O stretching vibrational modes in anions, respectively, due to the interaction of anions with the MXene surface in the first layer reducing their interaction with cations. The results of our research may potentially lead to the creation of novel energy storage devices that are eco-friendly, utilizing MXene electrodes and CBILs as electrolytes. © 2023 Elsevier B.V.
Journal of Physical Chemistry B (15205207)127(42)pp. 9111-9131
The behavior of nanodroplets of an imidazoliumbased dicationic ionic liquid, i.e., [C1(mim)2][PF6]2, was investigated in this study using ab initio molecular dynamics simulations. The vibrational features as well as the structural, interfacial, and dynamical properties of different sized droplets were analyzed and compared to the bulk phase system. Structural properties of the droplets, such as π-π stacking, radial distribution functions, structure factors, combined distribution functions, and angular distribution functions were analyzed to understand the interactions and orientations of their ions. The vibrational features and hydrogen bonding strength of droplets were studied by calculating their infrared (IR) and power spectra, determining the contribution of different types of hydrogen bonding to each vibrational mode. The calculated spectra showed good overall agreement with the experimental results. The interfacial properties of the droplets and the orientation of their ions were analyzed using density profiles and an exposed surface. The results showed that, in all systems studied, cations and anions were equally likely to exist in both inner and outer layers, and the cations tended to be oriented toward the center of droplets with obtuse angles. Additionally, the droplet densities were extrapolated to predict the bulk phase density with less than 2% deviation. The dynamical properties of hydrogen bonds, mean square displacement, and van Hove correlations of cations and anions were also analyzed. The results indicated that there was no regular trend in the dynamic properties of droplets with an increasing system size. © 2023 American Chemical Society.
Journal of Molecular Liquids (18733166)365
In this work, the effects of linkage alkyl chain length on the dynamical and structural micro-heterogeneities of some imidazolium-based dicationic ionic liquids (DILs) i.e. [Cn(mim)2][BF4]2, (n = 3, 6, 9, and 12) were studied via quantum mechanical calculations and also classical molecular dynamics (MD) simulations. Hydrogen bondings and also the interaction energies between the studied ions have been calculated using the density functional theory (DFT) calculations and also the quantum theory of atoms in molecules (QTAIM) method. The results showed that with increasing the linkage alkyl chain length of DILs, the interaction energies and electron densities are decreased, because the electrostatic interactions in DILs are weakened with increasing the –CH2 groups in the linkage chain. Different kinds of combined distribution functions (CDFs) were computed to better understand the orientations of ions in the studied DILs. Although, two rings of cation are almost perpendicular with respect to each other in all studied DILs, the orientation of linkage chain with respect to the rings is different in short- and long-linkage chain DILs. To understand the arrangement of the nearest neighboring ions, neighborhood analysis and spatial distribution functions (SDFs) of ions were analyzed. Furthermore, the mean square displacement (MSD), non-Gaussian parameter, van Hove correlation of cation and anions and also the ion pair, ion cage, hydrogen bond and reorientation dynamics were computed. DILs with longer alkyl chain length have more deviation in non-Gaussian parameter and Gaussian behavior of distribution of particle displacements, probably due to weakening the electrostatic interactions. Also, they have higher ion cage/ion pair stabilities than DILs with shorter linkage chain. Altogether, the linkage chain length in DILs has significant influences on their organizations in such a way that with increasing linkage chain length, their dynamical and structural micro-heterogeneities increase. © 2022 Elsevier B.V.
RSC Advances (20462069)12(54)pp. 35418-35435
A few studies on CO2 capture using dicationic ionic liquids (DILs) show that they are more promising absorbents for CO2 capture than monocationic ILs (MILs). Ion-ion, ion-CO2 and DIL molecule-CO2 interactions are important for understanding the performance-structure-property relationships for the rational design of DILs for CO2 capture applications. However, the role of these interactions in determining CO2 solubility in DILs is unclear. In this study, we used DFT methods to understand these interactions in three selected DILs)considering the effects of alkyl side chain length and symmetry in cations (by exploring different aspects, such as the electronic and geometrical structures, topological properties and the strength and nature of interactions, charge transfer, etc. The results showed that the most suitable solvent for CO2 is the symmetric DIL with a longer side chain length, i.e. [Bis(mim)C5-(C4)2][NTf2]2. In addition, we used the COSMO-RS calculations to obtain the macroscopic solubility of CO2 in the studied DILs, which was in good agreement with the DFT results. Gas selectivity results calculated using COSMO-RS theory indicated that the selectivity of CO2 from H2, CO and CH4 gases decreases slightly with increasing the length of side alkyl chains. © 2022 The Royal Society of Chemistry.
Journal of Molecular Liquids (18733166)330
In order to understand the role of cation symmetry in intra- and inter-molecular structures and dynamics of dicationic ionic liquids (DILs), we present the MD simulations and Voronoi tessellation analysis of two DILs including [C5(mim)2][NTf2]2 and [C5(tma)(mim)][NTf2]2. In this work, we systematically examined the effect of changing the electrostatic interactions on microheterogeneity (MH) by fixing the strength of the vdW interactions. The qualitative and quantitative analyses of the MH were explored through total/partial structure factors, heterogeneity order parameter (HOP) and domain analysis. Furthermore, radial distribution functions (RDFs), coordination numbers, spatial distribution functions (SDFs), neighborhood analysis of ions and combined distribution functions (CDFs) were calculated to determine the arrangement of the nearest neighboring ions. Local structural heterogeneity leads to local dynamical heterogeneity, which plays an important role in the applications related to ion transportation. To investigate dynamical heterogeneity, the mean square displacement, non-Gaussian parameter, van Hove correlation, and also the hydrogen bond, ion pair, ion cage and reorientation dynamics have been calculated. The results showed that the replacement of one imidazolium head of symmetrical [C5(mim)2]2+ cation with a trimethylammonium group shows significant effects on their structures and dynamics. © 2021 Elsevier B.V.
Fluid Phase Equilibria (03783812)548
This paper serves as a molecular dynamics (MD) study on the desulfurization of diesel oil model using magnetic ionic liquids (MILs). In this regard, three different MILs, namely, [emim][FeCl4], [bmim][FeCl4] and [hmim][FeCl4] have been used to remove the dibenzothiophene (DBT) from n-dodecane as diesel oil model. The effects of alkyl chain length of cation in MIL, temperature, initial sulfur content and mass ratio of MIL to diesel oil on two vital parameters of desulfurization process i.e. percentage of S-removal and Nernst partition coefficient (KN) were investigated. These two parameters were calculated based on the method proposed by Feng and Mi (Ind. Eng. Chem. Res. 2014, 53, 20234-20240), in which they used the radial distribution function (RDF) plots obtained by Conductor-like Screening Model for Real Solvents (COSMO-RS) to evaluate the desulfurization of fuel oil, quantitatively. Our results showed that the [bmim][FeCl4] has the highest DBT-philisity and its S-removal efficiency increases with increasing temperature and the concentration of the MIL. Furthermore, from the investigation of the initial sulfur content in diesel oil model it is concluded that the MIL can be a good extractor for oil refinery applications with a wide range of sulfur content in diesel oil. The results of RDF and combined distribution function (CDF) plots and also Voronoi tessellation analysis showed that the DBT molecules are adsorbed mainly by the MIL molecules compared with the n-dodecane which leads to DBT-removal. Also, it is found that the DBT molecules interact with the cation of MIL more than its anion. The results of domain analysis showed that the n-dodecane subset is stiffer than the MIL and DBT subsets. Altogether, the Fe-containing MILs can be a good sulfur extractor with high S-removal efficiency, lower toxicity than common volatile organic solvents, and low cost compared to the other common methods such as hydrodesulfurization (HDS), for future oil refinery applications. © 2021 Elsevier B.V.
Journal of Molecular Liquids (18733166)298
A molecular dynamics (MD) study on the behavior of some ion gels consists of two biodegradable aliphatic cholinium-based naphthenic acid ionic liquids (CBNAILs) confined in the BN nanostructures has been reported in this work. The structural and dynamical properties of these ILs between two h-BN nanosheets (h-BNNSs) as a function of intersheet separation were analyzed. Also, the confinement effects of these CBNAILs inside the BN nanotubes (BNNTs) as a function of nanotube diameter along with the solvation effects of these ILs outside the BNNTs were studied. The results of radial distribution functions (RDFs), number densities, charge densities, the number of hydrogen bonds, coordination numbers, mass density contours and also diffusion coefficients showed that how the structure and dynamics of these ILs changes under confinement conditions. Generally, the strength of ion−BN nanostructure interactions decreases with increasing nanopore size for both anions and cations and the dynamics of confined ions are slower than that of the bulk fluid, i.e. the ions move faster into the larger nanopores (h-BNNSs or BNNTs) than the smaller ones. The results have been compared with the recent studies of the adsorption of these ILs on one h-BN sheet and also with the behavior of confined aromatic CBNAILs. The results showed the ability of the biodegradable aliphatic CBNAILs to interact with BN nanosystems for developing specific applications such as super capacitors, lubricants, gas adsorption, dispersion of nanostructures, etc. © 2019 Elsevier B.V.
Physical Chemistry Chemical Physics (14639084)22(23)pp. 13070-13083
In this paper, we have reported a molecular dynamics (MD) study on the properties of three different magnetic imidazolium-based ionic liquids in the absence and presence of an external magnetic field. In this regard, the volumetric properties such as density and isobaric expansion coefficient, dynamical properties, namely, viscosity, mean square displacement of ions, diffusion coefficients, transport numbers of cations and anions, and electrical conductivity, and structural properties such as radial distribution function (RDF) and spatial distribution function (SDF) of [emim][FeCl4], [bmim][FeCl4] and [hmim][FeCl4] have been studied at different temperatures using molecular dynamics simulations. After studying the different volumetric, structural, and dynamical properties of the above-mentioned magnetic ILs in the absence of a magnetic field, we investigated the effect of an external magnetic field on the structural properties of one of these systems, i.e., [bmim][FeCl4]. In this regard, we established different contributions in the interactions between the external magnetic field and the studied magnetic ionic liquid (MIL). The number density profiles of the studied MIL before and after imposing an external magnetic field of 1.5 T showed a significant variation in the molecular distribution. The results indicated that the external magnetic field reduced the intensity of RDFs due to the reduction in the interactions between different ion sites as a result of changes in their orientations. After applying the external magnetic field, it was observed that due to the oppositely directed forces on the cations and anions, they moved in opposite directions. The snapshots showed that the static motion of the anion was smaller because of its small size. In the presence of an external magnetic field, the ions distributed more homogeneously compared to that observed in the absence of this field. The results of this study can be used in the rational and accurate design of viscomagnetic fluids and reaction systems in the presence and absence of magnetic fields. © the Owner Societies.
Physical Chemistry Chemical Physics (14639084)22(42)pp. 24431-24445
In this study, we extended the previously developed coarse-grained (CG) models of mono-cationic ionic liquids (MILs) to di-cationic ILs (DILs). To achieve this purpose, the MD simulations in three different mapping schemes of CG were done and the results of RDF (as a structural property), density (as a volumetric property) and the diffusion coefficient (as a dynamical property) were compared with the corresponding results of the all-atom (AA) simulations for [C5(mim)2][BF4]2. The previously developed CG models for MILs with the least refinement in parameters were used to extend the CG models for DILs. Since, the first mapping scheme of the CG model showed the best agreement with the results of the AA simulations for the three mentioned studied properties, this scheme was selected to simulate DILs using the CG model. The transferability of the selected CG model to DILs was investigated by comparing the different volumetric, structural and dynamical properties of [Cn(mim)2][BF4]2 (with n = 3, 6, 9, and 12) obtained from the CG model with those obtained using the corresponding atomistic simulations at different thermodynamic state points. The average deviation for the densities of the CG model with respect to the AA results is less than 2%. Furthermore, in both CG and AA models, the densities and isobaric expansion coefficients decrease with increasing temperature and linkage alkyl chain. The structural properties of the studied DILs, i.e. RDFs, nano segregation of domains, heterogeneity order parameters (HOPs) and angle distributions showed good agreements between the results of the CG and AA models. The CG-based calculated diffusion coefficients of the studied DILs at different temperatures showed that this model leads to faster dynamics with respect to the AA model due to the sacrifice of some degrees of freedom in this model. However, the trend of increasing diffusion coefficients with increasing temperature and linkage alkyl chain length is the same in both CG and AA models. Also, there are good agreements between the results of these two models for other dynamical properties, i.e. electrical conductivity, transference numbers and non-Gaussian parameter with increasing linkage alkyl chain and at various temperatures. © 2020 the Owner Societies.
Journal of Physical Chemistry B (15205207)124(50)pp. 11446-11462
The molecular dynamics simulations and Voronoi tessellation analysis of two dicationic ionic liquids (DILs) including [C5(mim)2][NTf2]2 and [C5(mim)2C4][NTf2]2 have been carried out to investigate the effects of side alkyl chain length on the structural and dynamical micro-heterogeneity of these DILs. Radial distribution functions (RDFs), spatial distribution functions (SDFs), and also neighborhood analysis of ions have been calculated to determine the arrangement of the nearest neighboring ions. To better understand the hydrogen-bonding network, microstructures, inter- and intramolecular orientations of ions in the studied DILs, different kinds of combined distribution functions (CDFs) were computed and analyzed. Also, qualitative and quantitative analyses of the structural heterogeneity were explored through total/partial structure factors, heterogeneity order parameters (HOPs), and domain analysis from Voronoi tessellation. The results showed that the side alkyl chains in DILs have significant effects on their micro-organizations in such a way that [C5(mim)2C4][NTf2]2 with longer side chains has more microstructural heterogeneity than [C5(mim)2][NTf2]2 where the linkage alkyl chain is the same in both of them. Furthermore, to shed light on the dynamical heterogeneity, ion pair, ion cage, and hydrogen-bond stabilities and also the reorientation dynamics of ions have been investigated. Results demonstrated that local dynamics differences originate from local structural heterogeneity. © 2020 American Chemical Society
Journal Of The Iranian Chemical Society (1735207X)16(12)pp. 2629-2637
In this work, four types of data mining methods, namely adaptive neuro-fuzzy inference system, artificial neural network—multilayer perceptron algorithm (ANN-MLP), artificial neural network—radial basis function algorithm (ANN-RBF), and group method of data handling (GMDH) have been used to predict the enhancement of the relative thermal conductivity of a wide range of nanofluids with different base fluids and nanoparticles. The total number of experimental data used in this work is 483 from 18 different nanofluids. The input parameters are thermal conductivity of base fluid and nanoparticles, volume fraction percent, the average size of nanoparticles, and temperature. Although the results showed that all four models are in relatively good agreement with experimental data, the ANFIS method is the best. The average absolute relative deviations (AARD%) between the experimental data and those of obtained using ANFIS, ANN-MLP, ANN-RBF, and GMDH methods were calculated as 2.7, 2.8, 4.2, and 4.3, respectively, for the test sets and as 1.1, 2.4, 3.9, and 4.5, respectively, for the training sets. Comparison between the predictions of the proposed ANN-MLP, ANN-RBF, ANFIS, and GMDH models and those predicted by traditional models, namely Maxwell and Bruggeman models showed that much better agreements can be obtained using the four models especially ANFIS model. Accordingly, the ANFIS method can able us to predict the relative thermal conductivity of new nanofluids in different conditions with good accuracy. © 2019, Iranian Chemical Society.
Journal of Physical Chemistry B (15205207)123(18)pp. 4070-4084
Amino acid choline-based ionic liquids (AACBILs) have high biodegradability, low toxicity, availability, low cost, and high thermal stability compared to the traditional ionic liquids (ILs). In this work, the volumetric, structural, and dynamical properties of three AACBILs, that is, choline alanine ([CH][Ala]), choline β-alanine ([CH][β-Ala]), and choline phenylalanine ([CH][Phe]) were investigated using the quantum mechanical calculations and also molecular dynamics simulations in both gas and liquid phases. The density functional theory calculations, noncovalent interactions, and also the quantum theory of atoms in molecules methods have been used to investigate the hydrogen bonds, interaction energies, and also charge transfers between the ions of the studied ILs. Density, isobaric expansion coefficient, mean square displacement (MSD), self-diffusivity, viscosity, electrical conductivity, and transference numbers have been computed for the studied AACBILs in different temperatures and at 0.1 MPa. There is a satisfactory agreement between the calculated data with the corresponding experimental values where they were available. Structural properties including radial distribution functions and spatial distribution functions of cations and anions were investigated. The results showed that because of the presence of an amine group away from the carboxylate group and also the absence of the planar phenyl group in the anion, the interactions between ionic pairs in [CH][β-Ala] are stronger than interactions between ions in [CH][Ala] and [CH][Phe]. The results showed that the order of diffusions and electrical conductivities is [CH][Ala] > [CH][β-Ala] > [CH][Phe], which can be interpreted by different electrostatic, van der Waals, and hydrogen interactions in these ILs. Our study provides considerable molecular insight into the structural features and dynamics of these biodegradable ILs. © 2019 American Chemical Society.
Journal of Chemical Physics (10897690)149(7)
The nanoscopic structure of biodegradable choline-based naphthenic acid ionic liquids near the hexagonal boron-nitride (h-BN) surface was analyzed using quantum mechanics calculations and molecular dynamics simulations. The effects of the type of the ring (aliphatic or aromatic) and the size of the ring in the anion counterpart of the aliphatic ionic liquids (ILs) on the configurations, binding energies, orbital energies, density of states, charge transfer, and thermochemistry of adsorption of ILs on the h-BN surface were investigated. Also the significance of non-covalent interactions on the adsorption of ILs was disclosed from the quantum theory of atoms in molecule. The results of radial distribution functions, number density, and also charge density profiles showed the existence of a solid-like bottom layer in the vicinity of the surface. Angular distribution functions revealed that while the most probable orientation in aromatic anions is parallel to the h-BN sheet, the most probable orientation in aliphatic rings apparently is perpendicular to the surface. The mobility of cations and anions in the studied ILs with respect to the h-BN sheet was analyzed using their mean square displacements. For all ions near the surface, dynamics in the parallel direction were faster than those in the z-direction due to the structuring of the solid-like layer of ILs near the h-BN surface. Altogether, this study provides new insights into the physisorption of this new class of biodegradable ILs on h-BN nanosheets at the molecular level. © 2018 Author(s).
Fluid Phase Equilibria (03783812)460pp. 135-145
To respond to the problems in experimental studies on the massive number of possible ionic liquids (ILs), the chemists and engineers try to develop the predictive models for different thermophysical properties of these compounds from the knowledge of their structures. In spite of monocationic ionic liquids (MILs), the available experimental data for multicationic ILs are scarce and often contradictory. In this work, simple group contribution methods (GCMs) were developed to estimate the density, surface tension and glass transition temperature of series of mono-, di-, and tri-cationic imidazolium-based ILs at ambient conditions. The studied ILs contain different anions and the number of carbon atoms in the alkyl chain of their cations vary from 2 to 12. The contribution of each of the structural groups in density and surface tension has been estimated based on the MILs with the lowest chain length i.e. MIL containing [C2mim]+ and also methyl and methylene groups based on the additivity of molar volumes and parachors. For glass transition temperature, the contributions proposed by Lazzus et al. for MILs (Thermochim. Acta 528 (2012) 38–44) were used. The results have been compared with the literature values where they exist. The proposed GCMs are easy to use and can extend to different mono- and multi-cationic ILs. Also, they can provide predictions of the property values for ILs which were never studied previously. The results showed that the method is successful in its predictions. The absolute average deviation, AAD%, for the density, surface tension and glass transition temperature of MILs are 0.31%, 2.48% and 0.56%, respectively. AAD% values of these properties for DILs are 0.71%, 5.37% and 3.07%, respectively. © 2017 Elsevier B.V.
Journal of Molecular Liquids (18733166)271pp. 96-104
In this study, three imidazolium-based linear tricationic ionic liquids (LTILs) have been studied using density functional theory (DFT) and also classical molecular dynamics simulation (MDS) to gain a deeper insight into their structures. Geometrical counterpoise (gcp) and D3 corrections were used to correct the electronic energies of the studied ions and LTILs and to interpret the unusual trends in their physical properties, i.e. their viscosities and melting points. To investigate the contributions of hydrogen bonds, dispersion interactions and steric effects to binding energies of LTILs, the NCI method which is based on the calculation of reduced density gradient (RDG) was used. The natural bond orbital (NBO) analysis has been also employed to study the H-bonding in the studied LTILs. A helical structure for the cations of the studied LTILs was observed as a result of strong network of different types of Hydrogen bonds. A non-polarizable all atom force field which is a refined version of Canongia Lopes and Paudua (CL&P) was adopted for the simulations. As well as the heterogeneity order parameter (HOP), the angular distribution functions of the angles of LTIL molecules have been used to describe the heterogeneity and spatial structure of the studied LTILs. The structural organization of the LTILs has been also compared with corresponding mono- and di-cationic ILs (MILs and DILs). © 2018 Elsevier B.V.
Physical Chemistry Chemical Physics (14639084)20(20)pp. 14251-14263
The surface properties of three symmetric linear tricationic ionic liquids (LTILs) with the common anion, bis(trifluoromethylsulfonyl)imide ([NTf2]-), were studied using atomistic molecular dynamics simulation and identification of the truly interfacial molecules (ITIM) analysis. A refined version of the CL&P force field with the partial charges based on quantum calculations for isolated ion quartets was used to calculate the number densities, orientation of the cations, charge densities and surface tensions. The densities obtained from the simulation of the interface are on average 3% smaller than the densities of bulk NPT simulations, which is due to applying long-range corrections in the simulations of bulk liquids. New observations were reported for this new class of ILs through density profiles and orientational analysis. The ITIM analysis shows that the surface of the LTILs is more populated with anions rather than cations and it becomes smoother with a decrease in the alkyl chain length of the cations. The microscopic structural analysis of the orientational ordering at the interface shows that although for LTIL-1 and LTIL-2, the surface is more populated with anions and therefore has a negative charge, for LTIL-3 the surface is more populated with linkage alkyl chains and therefore has a small positive charge. This difference in the interfacial structures arises from the difference in the alkyl chain lengths. The results show that the LTILs with shorter alkyl chains (i.e. n = 3 and 6) form an inverse-arc shape structure while LTILs with longer alkyl chains (i.e. n = 10) form a sinuous like structure at the interface. The surface tension values of these ILs were calculated at 298 K using the mechanical definition. The simulations resulted in acceptable values for surface tension compared to the experimental trends. © 2018 the Owner Societies.
Physical Chemistry Chemical Physics (14639084)20(1)pp. 435-448
In this work, the structural and dynamical properties of two imidazolium-based geminal dicationic ionic liquids (GDILs), i.e. [Cn(mim)2][NTf2]2 with n = 3 and 5, have been studied to obtain a fundamental understanding of the molecular basis of the macroscopic and microscopic properties of the bulk liquid phase. To achieve this purpose, molecular dynamics (MD) simulation, density functional theory (DFT) and atoms in molecule (AIM) methods were used. Interaction energies, charge transfers and hydrogen bonds between the cation and anions of each studied GDIL were investigated by DFT calculations and also AIM. The mean square displacement (MSD), self-diffusion coefficient, and transference number of the cation and anions, and also the density, viscosity and electrical conductivity of the studied GDILs, were computed at 333.15 K and at 1 atm. The simulated values were in good agreement with the experimental data. The effect of linkage alkyl chain length on the thermodynamic, transport and structural properties of these GDILs has been investigated. The structural features of these GDILs were characterized by calculating the partial site-site radial distribution functions (RDFs) and spatial distribution functions (SDFs). The heterogeneity order parameter (HOP) has been used to describe the spatial structures of these GDILs and the distribution of the angles formed between two cation heads and the middle carbon atom of the linkage alkyl chain was analyzed in these ILs. To investigate the temporal heterogeneity of the studied GDILs, the deviation of the self-part of the van Hove correlation function, Gs(r,t), from the Gaussian distribution of particle displacement and also the second-order non-Gaussian parameter, α2(t), were used. Since, the transport and interfacial properties and ionic characteristics of these GDILs were studied experimentally in our previous studies as a function of linkage chain length and temperature, in this work, we try to give a better perspective of the structure and dynamics of these systems at a molecular level. © 2018 the Owner Societies.
Journal of Physical Chemistry B (15205207)121(33)pp. 7946-7962
The structural and dynamical properties of two cholinium-based naphthenic acid ionic liquids (CBNAILs), namely, cholinium cyclopentane carboxylate ([CH][CPC]) and cholinium cyclohexane carboxylate ([CH][CHC]) have been studied using the classical molecular dynamics simulations and quantum mechanical methods. The results have also been compared with corresponding aromatic ones. Interaction energies, charge transfers, and hydrogen bondings between the studied ion pairs were investigated by density functional theory calculations and also the theory of atoms in molecules. Density, mean-square displacement, self-diffusivity, viscosity, electrical conductivity, transference number, ionicity, and fragility have been computed for the studied CBNAILs in the temperature range of 298.15-450 K and at 0.1 MPa. The simulated values were in good agreement with experimental data where they exist. The structural features of these CBNAILs were characterized by calculating the partial site-site radial distribution functions and spatial distribution functions. The results show a density cap of hydrogen atoms of hydroxyl groups of cations extended along the COO- groups of anions. In these ILs, [CPC]- and [CHC]- are connected by hydrogen bonding to [CH]+ mainly through the carboxylate group. Increasing the number of carbon atoms in the ring of [CHC]- with respect to [CPC]- makes remarkable changes in self-diffusions, electrical conductivities, and viscosities. Altogether, this work gives a better insight into the dynamics and structuring of this class of biodegradable ILs at a molecular level. © 2017 American Chemical Society.
Journal of Molecular Liquids (18733166)225pp. 810-821
Solvent systems composed of ionic liquid (IL) + poly(ethylene glycol) (PEG) provide “hybrid green” systems where “green meets green.” In this work, the density and viscosity of binary mixtures of 1-butyl-3-methylimidazolium tetrafluoroburate ([bmim][BF4]) and PEG with different number average molecular weights (i.e. 200, 400, 600, and 1000) were measured and analyzed as a function of temperature and composition. Excess molar properties of these mixtures were calculated and interpreted. A synergistic effect or super-viscosity was observed in the mixtures of [bmim][BF4] with PEG400, PEG600, and PEG1000 in which the mixture viscosity is higher than the viscosity of both pure components. By adding PEG to [bmim][BF4] in these mixtures, the decrease in the columbic attractive and van der Waals interactions is overcompensated by the formation of extensive H-bonding interactions which is responsible for observing the synergistic effect in the viscosity behavior of these mixtures. This effect can also influence on the excess properties. The FTIR spectroscopy was used for better analysis of molecular interactions. The variation in the positions and intensities of the peaks of FTIR spectra may be attributed to the possibility of H-bonding between C2 hydrogen of [bmim]+ and terminus [sbnd]OH as well as ethoxy [sbnd]O[sbnd] of PEG. © 2016 Elsevier B.V.
Journal of Chemical Thermodynamics (10963626)107pp. 1-7
Surface tensions and densities of three imidazolium-based geminal dicationic ionic liquids (GDILs) with the bis(trifluoromethylsulfonyl)imide, [NTf2]−, as a common anion, have been measured at ambient pressure at different temperatures in the range from 296.00 to 353.15 K. The surface thermodynamic functions such as surface entropy and surface enthalpy were derived from the temperature dependence of surface tension which indicated the surface ordering in these GDILs. As well as the parachor, the critical temperatures of these systems have been estimated using the Guggenheim and Eotvos correlations. In each case, the results of GDILs have been compared with the results of corresponding traditional monocationic ILs (MILs). Also, the relations between the surface tension and density and also surface tension and viscosity data have been demonstrated and discussed. © 2016 Elsevier Ltd
Journal of Physical Chemistry B (15205207)121(8)pp. 1877-1892
Three imidazolium-based linear tricationic ionic liquids (LTILs) have been simulated to study their structural and dynamical properties and obtain a fundamental understanding of the molecular basis of the microscopic and macroscopic properties of their bulk liquid phase. The effects of temperature and alkyl chain length on the physiochemical, transport, and structural properties of these LTILs have been investigated. A nonpolarizable all-atom force field, which is a refined version of the Canongia Lopes and Paudua force field, was adopted for the simulations. Densities, mean square displacements, self-diffusivities, viscosities, electrical conductivities, and transference numbers have been presented for various ions from MD simulations. The detailed microscopic structures have been discussed in terms of radial distribution functions and spatial distribution functions. The results show that, similar to that in monocationic and dicationic ILs (MILs and DILs, respectively), the anions are mainly organized around the imidazolium rings. The diffusion coefficients of the studied LTILs are smaller than those of both MILs and DILs, with comparable viscosities. Unlike those of MILs and DILs, the diffusion coefficients of the cations and anions of the studied LTILs increase with an increase in the length of the alkyl chain between the rings for LTIL-1 and LTIL-2 but then decrease for LTIL-3, which is in a good agreement with the trend of viscosity data. The calculated transference numbers show that, similar to that in MILs and DILs, cations have a major role in carrying electric current in LTILs, but this role increases from MILs to LTILs. © 2017 American Chemical Society.
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH (08885885)55(22)pp. 6517-6529
Proton nuclear magnetic resonance (H-1 NMR), diffusion-ordered NMR spectroscopy (DOSY-NMR), and ultraviolet-visible (UV-vis) spectroscopy techniques were used to study the specific intermolecular interactions within the binary mixtures of 1-butyl-3-methylimidazolium tetrafluoroburate, [bmim]BF4, and poly(ethylene glycol), PEG, with different average molecular weights (i.e., 200, 400, 600, and 1000) in the whole composition range. Also, the electrical conductivity and the viscosity of these four mixtures were measured at different compositions and temperatures. The results of 1H NMR spectra show that the change in proton chemical shifts of ionic liquid (IL) and PEG molecules in the mixtures is more than that of the pure ones. DOSY-NMR was used to measure the diffusion coefficients of the ionic species in the mixtures. Also, the other parameters such as hydrodynamic radii, transport numbers of anions and cations, and dissociation and association degrees of IL molecules were calculated from the diffusion coefficient and viscosity data. The overall results show that the behavior of the mixtures of [bmim]BF4 + PEG400, PEG600, and PEG1000 which show the synergistic effect on their viscosity is completely different from the IL + PEG200 mixture, and this difference can be interpreted well according to the special interactions occurring at the molecular level in these mixtures. Accordingly, in these mixtures, larger hydrodynamic radii and lower transport numbers of anions with respect to the cations may be attributed to the trapping of small anions in the polymeric clusters. Increasing the chain length and the concentration of PEG increases the association degree of the IL molecules due to increasing intermolecular interactions. The continuous decrement of electrical conductivity with increasing PEG concentration in these three mixtures confirms the cluster formation in the mixtures. The UV-vis spectra showed more hydrogen bonding interactions between unlike molecules in the mixtures containing higher molecular weight PEGs with respect to the lower ones.
Physics and Chemistry of Liquids (10290451)54(4)pp. 487-498
ABSTRACT: The major goal of this work is to apply the extended Lennard-Jones potential-based equation of state (ELJ-based EoS) to predict the density of five different classes of refrigerant systems including chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, hydrofluoroethers, perfluoroalkanes, and perfluoroalkylalkane. This EoS is based on an effective near-neighbor pair potential of the Lennard-Jones (12,6,3) type. The temperature dependencies of the parameters of the equation of state can be calculated at any temperature for each refrigerant. The calculated parameters along with the ELJ-based EoS have been used to calculate the density and isothermal compressibility coefficient of different refrigerants. A comparison between the predicted results and experimental data shows that the agreement is good. The total absolute average deviation of density for 14,871 data was found to be 0.34 compared with experimental data. Comparisons with the other EoSs show that the ELJ-based EoS is more accurate than other EoSs for most of the studied refrigerants. © 2015 Taylor & Francis.
Industrial and Engineering Chemistry Research (15205045)55(33)pp. 9087-9099
Some transport properties of imidazolium-based short alkyl chain length dicationic ionic liquids (DILs) ([Cn(mim)2][NTf2]2), including shear viscosity, diffusion coefficient, and electrical conductivity, have been measured and analyzed as a function of temperature and alkyl chain length. Also, the dependence of viscosity on shear rate has been investigated. The small intercepts of plots of shear stress versus shear rate and also the small variations of the viscosity values with changing shear rate show that the studied DILs are moderately non-Newtonian fluids. Temperature dependence of the viscosity of these ILs shows non-Arrhenius behavior which can be fitted well using four well-known equations, namely, power law, Litovitz, Vogel-Fulcher-Tammann (VFT), and Ghatee et al. equations. The activation thermodynamic parameters of these DILs were calculated. The positive values of Gibbs free energy of activation show that the slip of two layers of the fluid is a nonspontaneous process. DOSY NMR spectroscopy was used to measure the diffusion coefficients of the ionic species in these DIL systems. Also, the other parameters such as hydrodynamic radii and transport numbers of anions and cations and dissociation and association degrees of IL molecules were calculated from the diffusion coefficient and viscosity data. We measured the electrical conductivity of these ILs at different temperatures. The ionicity of these DILs which was evaluated using the Walden plot diagnostic showed that these fluids are "subionic". With the help of the m-fragility parameter, we measured the fragility of these fluids and indicated that these DILs are in the intermediate to fragile range. Also, we showed a correlation between the m-fragility and the ionicity of these ILs. © 2016 American Chemical Society.
Physics and Chemistry of Liquids (10290451)53(3)pp. 360-375
In this work, the extended Lennard-Jones potential-based equation of state (ELJ-based EoS) on which the effective near-neighbour pair interactions are LJ (12,6,3) type has been used to predict the specific volume and other thermodynamic properties of some semi-crystalline and liquid polymers and copolymers up to extremely high temperature–high pressure conditions. It seems that, at least in the dense regions, there are no upper- and lower-specific volume limitations in the applicability of the model for different polymeric systems. The parameters can be determined at any temperature for each compound using the temperature dependence of the parameters of ELJ-based EoS. The calculated parameters have been used to calculate the specific volume and other derived thermodynamic properties of different polymeric systems at any temperature and pressure. The ELJ-based EoS has been also compared with some previous studies. © 2014, © 2014 Taylor & Francis.
Journal of Molecular Liquids (18733166)209pp. 693-705
Abstract In this work, the shear-, temperature- and composition-dependencies of the viscosity of binary mixtures of 1-butyl-3-methylimidazolium hexafluorophosphate with methanol {[bmim]PF6 + methanol} have been studied. The results showed that adding alcohol causes a gradual change in the behavior of the mixtures from moderate non-Newtonian (in pure ionic liquid) to Newtonian (in pure alcohol) over a wide range of shear rate ((14 to 56.0) s- 1) in the temperature range of (283.15 to 333.15) K. The activation parameters, namely, ΔH∗ (enthalpy of activation), ΔG∗ (free energy of activation), ΔS∗ (entropy of activation), and ΔC∗p (change in heat capacity of activation) for their viscous flow were evaluated. The values of ΔH∗ and ΔS∗ nicely compensated each other. The temperature and composition dependencies of viscosities have been fitted using proper equations. Also, the law of corresponding states can be seen in the viscosity behavior of these mixtures based on two different equations. The excess molar properties were calculated from the experimental data and the Redlich-Kister polynomial equation was used to fit these data. An artificial neural network (ANN) method has been developed to model simultaneously the shear-, temperature- and composition- dependencies of the viscosities of these mixtures. © 2015 Elsevier B.V.
Fluid Phase Equilibria (03783812)361pp. 135-142
In this study, the application of artificial neural network (ANN) method in predicting the density of alkali metals and their mixtures is investigated. A total number of 595 different data points of these compounds were used to train, validate and test the model. A typical three-layer feedforward backpropagation neural network has been trained by the Levenberg Marquardt algorithm. The tansig-tansig transfer functions with 15 neurons in the hidden layer makes the least error, so a network with (8-15-1) structure was used to design the ANN model. The average relative deviations for train, validation, and test sets are 0.1029, 0.1396, and 0.1002, respectively. A comparison between our results and those obtained from some previous works shows that this work, as an excellent alternative, can provide a simple procedure to predict the density of these compounds in a better accord with experimental data up to high temperature, high pressure (HTHP) conditions. © 2013 Elsevier B.V.
Journal of Molecular Liquids (18733166)190pp. 59-67
The shear- and temperature-dependency of the viscosity of two imidazolium-based ionic liquids namely, 1-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF6] and 1-butyl-3-methylimidazolium nitrate, [bmim][NO3], has been studied in this work. The experimental results showed that the viscosity of these fluids decreases with increasing temperature. The results also showed that these ionic liquids are non-Newtonian over a wide range of shear rate ((14 to 56.0) s- 1) in the temperature range of (283.15 to 343.15) K and their shear viscosity depends strongly on temperature. The activation parameters, namely, ΔH â (enthalpy of activation), ΔGâ (free energy of activation), ΔSâ (entropy of activation), and ΔCpâ (change in heat capacity of activation) values for their viscous flow were evaluated. The magnitudes of the parameters were fairly large. The values of all these parameters decreased with temperature. The values of ΔHâ and ΔS â nicely compensated each other. The temperature dependence of viscosities was fitted using the power law, Litovitz, Vogel-Fulcher-Tammann (VFT), and Ghatee et al. equations. Also, the law of corresponding states can be seen in the viscosity behavior of these ILs based on two different equations. © 2013 Elsevier B.V.
International Journal of Refrigeration (01407007)48pp. 188-200
In this work, the densities of 48 refrigerant systems from 5 different categories including hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), hydrofluoroethers (HFEs), perfluoroalkanes (PFAs), and perfluoroalkylalkanes (PFAAs) have been studied using a combined method that includes an artificial neural network (ANN) and a simple group contribution method (GCM). A total of 3825 data points of liquid density at several temperatures and pressures have been used to train, validate and test the model. This study shows that the ANN-GCM model represents an excellent alternative to estimate the density of different refrigerant systems with a good accuracy. The average absolute deviations for train, validation, and test sets are 0.18, 0.26, and 0.28, respectively. A comparison between our results and those obtained from some previous methods shows that as well as generality, this model can predict the density of different refrigerants in a better accord with experimental data up to high temperature, high pressure (HTHP) conditions. © 2014 Elsevier Ltd and IIR. All rights reserved.
Moosavi, M.,
Daneshvar, A.,
Sedghamiz, E.,
Momtaz, E.,
Joharian, A. Journal of Molecular Liquids (18733166)199pp. 257-266
The shear rate-, temperature- and composition-dependencies of the viscosity of binary mixtures of 1-butyl 3-methylimidazolium nitrate with ethanol {[bmim]NO3(x) + ethanol} have been studied in this work. The results showed that these mixtures are non-Newtonian over a wide range of shear rate ((14 to 56.0) s- 1) in the temperature range of 283.15 to 333.15 K and over all composition range. The activation parameters, namely, ΔH∗(enthalpy of activation), ΔG∗(free energy of activation), ΔS∗(entropy of activation), and ΔCp∗(change in heat capacity of activation) for their viscous flow were evaluated. The values of ΔH∗and ΔS∗nicely compensated each other. The temperature and composition dependencies of viscosities have been fitted using proper equations. Also, the law of corresponding states can be seen in the viscosity behavior of these mixtures based on two different equations. The excess molar properties were calculated from the experimental data and the Redlich-Kister polynomial equation was used to fit these data. An artificial neural network (ANN) method has been developed to model simultaneously the shear-, temperature- and composition-dependencies of the viscosities of these mixtures. © 2014 Elsevier B.V.
Physics and Chemistry of Liquids (10290451)52(2)pp. 291-304
In this work, the extended Lennerd-Jones potential-based equation of state (ELJ-based EoS) on which the effective near-neighbour pair interactions are LJ (12,6,3) type has been extended to predict the density and other thermodynamic properties of quantum light molecules in subcritical (liquid) and supercritical regions. There are no upper and lower density limitations in the applicability of the model for these systems. Having the temperature dependence of the parameters of new EoS, the parameters can be determined at any temperature for each of quantum light molecules, including H2, p-H2, D2, He, and Ne. A comparison with literature data has been made. The results show that the ELJ-based EoS can be used to predict the density and other thermodynamic properties of quantum light molecules within experimental errors. The average absolute deviations for density are better than 0.2% in the subcritical region and 0.12% in the supercritical region for all studied molecules. © 2013 © 2013 Taylor & Francis.
Journal of Molecular Liquids (18733166)184pp. 17-23
In the previous studies, the GMA (Goharshadi-Morsali-Abbaspour) equation has been extended to the long chain n-alkanes, alcohols, amines, ketones, 1-carboxylic acids and esters via the group contribution method (GCM). The new proposed equation was named GCM-GMA equation. In this work, we have extended the GCM-GMA equation to predict the molar density of long chain ethers and glycol ethers and the binary and ternary mixtures of different organic compounds with ethers and glycol ethers. Each of these organic compounds has been assumed as a hypothetical mixture of methyl, methylene, and a functional group. Then, the GMA equation has been modified for such a hypothetical mixture. Propane, n-butane, n-hexane, 1-pentanol, 2-pentanol, and diethyl ether have been used to investigate the contribution of the different segments in the GCM-GMA equation parameters. The calculated parameters along with the GCM-GMA equation have been used to calculate the molar density of different long chain ethers and glycol ethers and their binary and ternary mixtures. The values of statistical parameters between experimental and calculated density show the ability of this equation to predict the density of these organic compounds. The GCM-GMA equation has been compared with four cubic equations of state. The results show that the GCM-GMA gives better results than other methods. Also, the excess molar volumes of some binary mixtures have been calculated from the density data at different temperatures. © 2013 Elsevier B.V. All rights reserved.
Thermochimica Acta (00406031)556pp. 89-96
In this work, the densities of hydrocarbon systems have been estimated using a combined method that includes an artificial neural network (ANN) and a simple group contribution method (GCM). A total of 2891 data points of density at several temperatures and pressures, corresponding to 40 different hydrocarbons including short- and long-chain alkanes ranging from CH4 to n-C40H82, and also several cycloalkanes, highly branched alkanes and aromatic hydrocarbons have been used to train, validate and test the model. This study shows that the ANN-GCM model represent an excellent alternative for the estimation of the density of hydrocarbons with a good accuracy. A wide comparison between our results and those of obtained from some previous methods shows that this work can provide a simple procedure for prediction the density of different classes of hydrocarbons in a better accord with experimental data up to high temperature, high pressure (HTHP) conditions. © 2013 Elsevier B.V.
Fluid Phase Equilibria (03783812)356pp. 176-184
In this work, the specific volumes of some polymeric systems have been estimated using a combined method that includes an artificial neural network (ANN) and a simple group contribution method (GCM). A total of 2865 data points of specific volume at several temperatures and pressures, corresponding to 25 different polymeric systems have been used to train, validate and test the model. This study shows that the ANN-GCM model represent an excellent alternative for the estimation of the specific volume of different polymeric systems with a good accuracy. The average relative deviations for train, validation, and test sets are 0.0403, 0.0439, and 0.0482, respectively. A wide comparison between our results and those of obtained from some previous methods show that this work can provide a simple procedure for prediction the specific volume of different polymeric systems in a better accord with experimental data up to high temperature, high pressure (HTHP) conditions. © 2013 Elsevier B.V.
Journal of Molecular Liquids (18733166)174pp. 117-123
A new proposed equation of state (EoS) for pure liquid alkali metals has been extended to predict the volumetric and thermodynamic properties of alkali metal alloys at different temperatures, pressures, and compositions. The new equation which is valid over the whole liquid range is based on a suggested potential function and the interactions of nearest neighbors are according to the characteristics of the soft repulsive interaction in dense and large attractive interaction in expanded liquid alkali metals. The composition dependencies of the parameters of the equation of state are assumed as quadratic functions of mole fraction considering the mean geometry approximation MGA. In this paper, the calculated results of liquid density and other thermodynamic properties such as isobaric expansion coefficient, α P, isothermal compressibility, κ T, and internal pressure, P i, of binary molten alloys of Na-K and Cs-K from the freezing point up to several hundred degrees above the boiling point are presented. The results show good agreement between the density values obtained from this equation and the experimental and literature data. To show the ability of this EoS in prediction of density of alkali metal alloys, the results have been compared with some other equations. Although there is no corresponding literature data to compare the results obtained for derived thermodynamic properties, the variations of these properties with temperature and composition show proper trends for these alloys. © 2012 Elsevier B.V.
Fluid Phase Equilibria (03783812)329pp. 63-70
In this paper, we have derived an equation of state (EoS) for liquid alkali metals based on a suggested potential function over the whole liquid range including metal-nonmetal transition. This EoS is based on the interaction of nearest neighbors according to the characteristics of the soft repulsive interaction in dense and large attractive interaction in expanded liquid alkali metals. PVT data of dense liquid alkali metals obey the equation (2Z-1)V m=A+Bρ over the whole range of liquid densities, where Z, V m, and ρ are compression factor, molar volume, and molar density, respectively. The intercept A and slope B of this equation are related to the attractive and repulsive parts of suggested potential function, respectively, and both depend on temperature. The new EoS has been used to calculate the molar density and other thermodynamic properties such as isobaric expansion coefficient, α P; isothermal compressibility, κ T; and internal pressure, P i; of liquid alkali metals at any temperature and pressure over the whole liquid range. The results show good agreement between the values obtained using this equation and the experimental and literature data. To show the ability of this EoS in prediction of thermodynamic properties of liquid alkali metals over the whole liquid range, the results have been compared with some other equations. © 2012 Elsevier B.V.
Journal of Supercritical Fluids (08968446)68pp. 71-80
In this work, the extended Lennard-Jones potential-based equation of state (ELJ-based EoS) on which the effective near-neighbor pair interactions are LJ (12,6,3) type has been extended to predict the density and other thermodynamic properties of hydrocarbons up to extremely high temperature, high pressure (HTHP) conditions. It seems that, at least in the dense regions, there are no upper and lower density limitations in the applicability of the model for different hydrocarbon systems. Having the temperature dependence of the parameters of new EoS, the parameters can be determined at any temperature for each of 38 studied compounds, including short- and long-chain alkanes ranging from CH 4 to n-C 40H 82, and also several cycloalkanes, highly branched alkanes and aromatic hydrocarbons. The calculated parameters have been used to calculate the density and other derived thermodynamic properties of different hydrocarbons at any temperature and pressure. The results show that ELJ-based EoS is clearly superior to those obtained using previous works in accord with experimental data up to HTHP conditions. © 2012 Elsevier B.V. All rights reserved.
Fluid Phase Equilibria (03783812)316pp. 122-131
In the previous works, the GMA (Goharshadi-Morsali-Abbaspour) equation was extended to the long-chain n-alkanes, alcohols, amines, and ketones based on the group contribution method (GCM). This new equation was called GCM-GMA equation. In this work, the GCM-GMA equation has been extended to predict the molar density and other thermodynamic properties of long chain 1-carboxylic acids and esters and the binary and ternary mixtures of different organic compounds. Each of these organic compounds has been assumed as a hypothetical mixture of methyl, methylene, and a functional group. Then, the GMA equation has been modified for such a hypothetical mixture. Propane, n-butane, n-hexane, and also 1-pentanoic acid and n-butyl acetate have been used as basic compounds to obtain the contribution of different segments in the GCM-GMA equation parameters. The calculated parameters along with the GCM-GMA equation have been used to calculate the molar density and other thermodynamic properties such as isobaric expansion coefficient, α P, isothermal compressibility, κ T, and internal pressure, P i, of different compounds at any temperature, pressure, and mole fraction. The results show good agreement between the values obtained by GCM-GMA equation and the experimental and literature data. To show the ability of this equation in prediction of molar density, the calculated densities have been compared with some other equations. The results show that the GCM-GMA equation gives better results than other methods. © 2011 Elsevier B.V.
Thermochimica Acta (00406031)526(1-2)pp. 35-45
In this work, the linear isotherm regularity equation of state (LIR EoS) has been extended to predict the molar density of long chain primary and secondary amines, and esters and also the binary and ternary mixtures containing different functional groups. Each of these organic compounds has been assumed as a hypothetical mixture of methyl, methylene, and a functional group. Then, the LIR EoS has been modified for such a hypothetical mixture (MLIR EoS). Propane, n-butane, cyclohexane, 1-pentylamine, 2-aminobutane and n-butyl acetate have been used to investigate the contribution of the different segments in the new EoS parameters. The calculated parameters along with the MLIR EoS have been used to calculate the molar density and other thermodynamic properties of different pure compounds and their binary and ternary mixtures. A wide comparison has been made with some other EoSs and correlations. The results show that the MLIR EoS gives better results than other methods in accord with experimental data. © 2011 Elsevier B.V. All rights reserved.
Fluid Phase Equilibria (03783812)310(1-2)pp. 63-73
In the previous work [21], the GMA (Goharshadi-Morsali-Abbaspour) equation was extended to the long-chain n-alkanes based on the group contribution method (GCM). This extended equation was called GCM-GMA equation. In this work, the GCM-GMA equation has been extended to predict the density and other thermodynamic properties of primary, secondary and tertiary alcohols, primary and secondary amines, and ketones and their binary and ternary mixtures. Each of these organic compounds has been assumed as a hypothetical mixture of methyl, methylene, and a functional group. Then, the GCM-GMA equation has been modified for such a hypothetical mixture. Propane, n-butane, n-hexane, and also 1-pentanol, 2-pentanol, 2-methyl-2-propanol (t-BuOH), 1-pentylamine, 2-aminobutane, and 2-pentanone have been used as basic compounds to obtain the contribution of different segments in the GCM-GMA equation parameters. The calculated parameters along with the GCM-GMA equation have been used to calculate the density and other thermodynamic properties such as isobaric expansion coefficient, αP, isothermal compressibility, κT, and internal pressure, Pi, of different compounds at any temperature, pressure, and mole fraction. The results show good agreement between the values obtained by the GCM-GMA equation and the experimental and literature data. To show the ability of this equation in prediction of density, the calculated densities have been compared with some other equations. The results show that the GCM-GMA equation gives better results than other methods in accord with experimental data. © 2011 Elsevier B.V.
Goharshadi, E.K.,
Abareshi, M.,
Mehrkhah, R.,
Samiee, S.,
Moosavi, M.,
Youssefi, A.,
Nancarrow, P. Materials Science in Semiconductor Processing (13698001)14(1)pp. 69-72
A convenient microwave method in preparation of zinc oxide nanoparticles (ZnONPs) using an ionic liquid, trihexyltetradecylphosphonium bis{(trifluoromethyl)sulfonyl}-imide, [P66614][NTf2], as a green solvent is described in this paper. To the best of our knowledge, there is no report for synthesizing any nanoparticle using this ionic liquid. Trihexyltetradecylphosphonium bis{(trifluoromethyl)sulfonyl}-imide has low interface tension and thus it can enhance the nucleation rate, which is favorable to the formation of smaller ZnONPs. The fabricated ZnONPs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-vis spectroscopy. The XRD pattern reveals that the ZnONPs have hexagonal wurtzite structure. The strong intensity and narrow width of ZnO diffraction peaks indicate that the resulting nanoparticles are of high crystallinity. The synthesized ZnONPs show direct band gap of 3.43 eV. The UVvis absorption spectrum of ZnONPs dispersed in ethylene glycol at room temperature revealed a blue-shifted onset of absorption. © 2010 Elsevier Ltd. All rights reserved.
Industrial and Engineering Chemistry Research (15205045)49(14)pp. 6662-6669
In this work, the group contribution method has been applied in combination with the Goharshadi-MorsaliAbbaspour (GMA) equation of state (EoS) to calculate the density of η-alkanes and their binary and ternary mixtures. Each normal alkane has been considered as a hypothetical mixture of methyl and methylene groups in which the interaction potential between each pair is assumed to be the average effective pair potential (AEPP). The GMA EoS has been modified for n-alkanes according to the group contribution method (GCM), and the new regularity is called GCM-GMA EoS. Propane, n-butane, and n-hexane have been used as basic compounds to investigate the contribution of each carbonic (methyl and methylene) group in the new EoS parameters. The calculated parameters along with GCM-GMA EoS have been used to calculate the density of n-alkanes and their binary and ternary mixtures at different temperatures, pressures, and compositions. The results in the prediction of density show good agreement with experimental data. To show the ability of this equation of state in the prediction of density, the calculated densities of some liquid mixtures have been compared with those computed from original GMA EoS according to mixing and combining rules and also with the COSTALD method. The GCM-GMA EoS have been also compared with four cubic equations of state, namely, RM (Riazi-Mansoori), RK (Redlich-Kwong), SRK (Soave-Redlich-Kwong), and PR (PengRabinson). The results show that the group contribution method gives better results than other methods. © 2010 American. Chemical Society.
International Journal of Heat and Fluid Flow (0142727X)31(4)pp. 599-605
ZnO nanofluids have been prepared by dispersing ZnO nanoparticles in the ethylene glycol (EG) and glycerol (G) as the base fluids. Ammonium citrate, as a dispersant, has been used to improve the dispersion of nanoparticles and suppressing formation of particle clusters to obtain stable suspensions.The thermal conductivity of ZnO nanofluids has been measured as a function of the volume fraction and temperature. The thermal conductivity of ZnO/EG and ZnO/G nanofluids increases nonlinearly up to 10.5% and 7.2%, respectively, as the volume fraction of nanoparticles increases up to 3. vol.%. The thermal conductivity of a ZnO nanofluid increases nonlinearly with increasing the temperature at a constant volume fraction of nanoparticles.For the first time, we have measured the viscosity and surface tension of ZnO nanofluids. The viscosity ratio of nanofluids increases with increasing concentration and decreasing the temperature. The surface tension ratio of suspensions containing solid particles increases with increasing the volume fraction of the solid nanoparticles.The experimental data for thermal conductivity and viscosity have been compared with some existing theoretical models. © 2010 Elsevier Inc.
Jalal, R.,
Goharshadi, E.K.,
Abareshi, M.,
Moosavi, M.,
Yousefi, A.,
Nancarrow, P. Materials Chemistry and Physics (02540584)121(1-2)pp. 198-201
Zinc oxide nanoparticles have been synthesized by microwave decomposition of zinc acetate precursor using an ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide, [bmim][NTf2] as a green solvent. The structure and morphology of ZnO nanoparticles have been characterized using X-ray diffraction and transmission electron microscopy. The ZnO nanofluids have been prepared by dispersing ZnO nanoparticles in glycerol as a base fluid in the presence of ammonium citrate as a dispersant. The antibacterial activity of suspensions of ZnO nanofluids against (E. coli) has been evaluated by estimating the reduction ratio of the bacteria treated with ZnO. Survival ratio of bacteria decreases with increasing the concentrations of ZnO nanofluids and time. The results show that an increase in the concentrations of ZnO nanofluids produces strong antibacterial activity toward E. coli. © 2010 Elsevier B.V. All rights reserved.
Fluid Phase Equilibria (03783812)274(1-2)pp. 51-58
Molecular dynamics (MD) has been performed to compute the pressure and internal energy of binary mixtures of argon-neon, argon-krypton, and argon-xenon at different temperatures and compositions using two-body Hartree-Fock dispersion-like (HFD-like), total (two-body + three-body) HFD-like, and Lennard-Jones (LJ) potentials. The results are in a good overall agreement with the experimental data. To elucidate the role of three-body interactions on the thermodynamic properties of the studied mixtures, we have incorporated Wang and Sadus method into MD simulations performed using density-dependent two-body HFD-like potentials. Much better results for pressure have been obtained at high densities using the effective LJ potential. For the second virial coefficient, the HFD-like potential is a better choice. Since a little attention has been paid to the qualitative analysis of RDF in the liquid mixtures so far, we have also analyzed the variation of radial distribution function (RDF) of the mixtures with density and composition. © 2008 Elsevier B.V. All rights reserved.
International Journal of Thermophysics (15729567)29(2)pp. 656-663
In this work, a simple equation of state (EoS) has been used to predict some thermodynamic properties of air as a pseudo-pure fluid; as a ternary mixture of nitrogen, oxygen, and argon; and as a binary mixture of nitrogen and oxygen at different temperatures and pressures. A comparison with literature tabulated values has been made. The agreement of calculated densities with corresponding tabulated values is good for which the average absolute deviations are better than 0.06% if we assume air as a pseudo-pure fluid, and 0.9% and 1.2% if we consider air as a ternary mixture and as a binary mixture, respectively. To show the ability of this equation of state to predict density, the calculated densities of air have been compared with those computed by other methods. © 2008 Springer Science+Business Media, LLC.
Journal of Molecular Liquids (18733166)142(1-3)pp. 41-44
In this work, we have used a simple equation of state (EoS) to predict the density and other thermodynamic properties such as isobaric expansion coefficient, αP, isothermal compressibility, κT, and internal pressure, Pi, for nine ionic liquids including trihexyl (tetradecyl) phosphonium chloride ([(C6H13)3P(C14H29)][Cl]), trihexyl (tetradecyl) phosphonium acetate ([(C6H13)3P(C14H29)][Ac]), trihexyl (tetradecyl) phosphonium bis {(trifluoromethyl) sulfonyl} amide ([(C6H13)3P(C14H29)][NTf2]), 1-butyl-3-methylimidazolium bis {(trifluoromethyl) sulfonyl} amide ([bmim][NTf2]), 1-hexyl-3-methylimidazolium bis {(trifluoromethyl) sulfonyl} amide ([hmim][NTf2]), 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), 1-butyl-3-octylimidazolium tetrafluoroborate ([omim][BF4]), 1-butyl-3-octylimidazolium hexafluorophosphate ([omim][PF6]), and 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) at different temperatures and pressures. A wide comparison with experimental and literature data has been made. The results show that this EoS can be used to reproduce and predict different thermodynamic properties of ionic liquids within experimental errors. © 2008 Elsevier B.V. All rights reserved.
International Journal of Thermal Sciences (12900729)46(9)pp. 944-952
In this work, we have used a simple equation of state (EoS) to calculate the density of five lubricant/refrigerant mixtures including octane/dimethyl carbonate, TriEGDME/HFC-134a, TEGDME/HFC-134a, heptane/TEGDME, and decane/dimethyl carbonate at different temperatures, pressures, and compositions. The excess molar volumes of these mixtures have been calculated using this equation of state. Also, we have computed other thermodynamic properties such as isobaric expansion coefficient, isothermal compressibility, and internal pressure, for octane/dimethyl carbonate system for which the corresponding experimental values are available. A wide comparison with experimental data has been made for each thermodynamic property. The values of statistical parameters between experimental and calculated properties show the ability of this equation of state in reproducing and calculating of different thermodynamic properties for studied mixtures. © 2006.
Thermochimica Acta (00406031)447(1)pp. 64-68
A new general equation of state recently reported for pure liquids has been developed to predict the volumetric and thermodynamic properties of six binary and two ternary liquid refrigerant mixtures (including HCs and HFCs mixtures) at different temperatures, pressures, and compositions. The results show this equation of state can be used to reproduce and predict different thermodynamic properties of liquid refrigerant mixtures within experimental errors. The composition dependence of the parameters of this equation of state has been assumed as quadratic functions of mole fraction. Using these mixing rules, the agreement between calculated and experimental densities is better than 0.6% for binary mixtures and 2.3% for ternary mixtures. To compare the performance of this new equation of state against other well-known methods such as the COSTALD method, the density of some refrigerant mixtures, for which the parameters of COSTALD were available, has been computed and compared with those of this new equation of state. © 2006 Elsevier B.V. All rights reserved.
Fluid Phase Equilibria (03783812)245(2)pp. 109-116
The density of nine binary and two ternary liquid mixtures at different temperatures, pressures, and compositions has been calculated using a new equation of state considering mean geometry approximation "MGA". Although the studied mixtures cover the vast variety of mixtures including the inert gases, polar, nonpolar, refrigerant, and strongly hydrogen-bonded systems, the results in prediction of density show good agreement with experiment. The excellent results have been obtained whenever the size and the strength of intermolecular forces of components in a mixture are very similar. Our results show that the effect of size is more important than that of the strength of intermolecular forces. Since the strength of hydrogen bonding in the system of water/methanol is very high, the agreement of calculated densities with the corresponding experimental values is interesting for which the average absolute deviations are better than 1%. To show the ability of this equation of state in prediction of density, the calculated densities of some liquid mixtures have been compared with those of computed from other equations of state. © 2006 Elsevier B.V. All rights reserved.
International Journal of Thermophysics (15729567)27(5)pp. 1515-1526
In this work, a simple equation of state (EoS) has been used to predict the density and other thermodynamic properties such as the isobaric expansion coefficient, α P , the isothermal compressibility, κ T , and the internal pressure, P i , of six glycol ethers including diethylene glycol monobutyl ether (DEGBE), propylene glycol propyl ether (PGPE), diethylene glycol monomethyl ether (DEGME), diethylene glycol monoethyl ether (DEGEE), triethylene glycol dimethyl ether (TriEGDME), and tetraethylene glycol dimethyl ether (TEGDME) at different temperatures and pressures. A comparison with literature experimental data has been made. Additionally, statistical parameters between experimental and calculated densities for the GMA EoS and four other EoSs (Soave-Redlich-Kwong, Peng-Robinson, Soave-Redlich-Kwong with volume translation, and Patel-Teja) indicate the superiority of the GMA EoS. © Springer Science+Business Media, LLC 2006.
Industrial and Engineering Chemistry Research (15205045)44(17)pp. 6973-6980
A new equation of state recently reported for pure liquids has been extended to predict the volumetric and thermodynamic properties of 10 binary mixtures and 1 ternary liquid mixture at different temperatures, pressures, and compositions. A wide comparison with literature experimental data shows the ability of this equation of state to reproduce and predict different volumetric and thermodynamic properties of liquid mixtures. For the binary and ternary mixtures, the composition dependences of the parameters of the equation of state are assumed as quadratic functions of mole fraction. Using these mixing rules, the agreement between the calculated and experimental densities is better than 0.8% for binary mixtures and 3.1% for ternary mixtures. © 2005 American Chemical Society.
