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International Journal of Thermophysics (15729567)18(5)pp. 1197-1216
A general equation of state, originally proposed for compressed solids by Parsafar and Mason, has been successfully applied to dense fluids. The equation was tested with experimental data for 13 fluids, including polar, nonpolar, saturated and unsaturated hydrocarbons, strongly hydrogen bonded, and quantum fluids. This equation works well for densities larger than the Boyle density ρB [1/ρB = TB dB2(TB)/dT, where B2(TB) is the second virial coefficient at the Boyle temperature, at which B2 = 0] and for a wide temperature range, specifically from the triple point to the highest temperature for which the experimental measurements have been reported. The equation is used to predict some important known regularities for dense fluids, like the common bulk modulus and the common compression points, and the Tait-Murnaghan equation. Regarding the common points, the equation of state predicts that such common points are only a low-temperature characteristic of dense fluids, as verified experimentally. It is also found that the temperature dependence of the parameters of the equation of state differs from those given for the compressed solids. Specifically they are given by Ai(T) = ai + biT + ciT2 - diT ln(T).
Journal of Physical Chemistry B (15205207)101(42)pp. 8578-8583
In the present work the existence of a common compression factor point for binary mixtures has been investigated, both experimentally and theoretically. We found that the linear isotherm regularity (LIR) is able to predict the common compression factor point and the common bulk modulus point for binary mixtures, as well as pure dense fluids. An important conclusion deduced from this work is that a physical interpretation for such points may be given using LIR. The LIR along with the mean geometric approximation (MGA) have been used to relate the density at the common points of a mixture to those of its pure components. The numerical investigation shows that such a relation may be represented by a quadratic function in terms of the system composition for most mixtures. However, we have found that such a quadratic relation is generally valid for all investigated mixtures. An important result obtained from this work is that we may get information about the magnitude of interactions between unlike molecules, compared to those of like interactions. Such a result can be used to predict the deviation of a solution from ideality without having any vapor pressure data.
Journal of Physical Chemistry A (15205215)107(33)pp. 6476-6482
Electronic, structural, and spectroscopic properties of the ground-state neutral and singly ionized mono-, di-, tri-, and tetrafluoropyrroles are studied using ab initio and density functional theory quantum mechanical methods. The effects of the number and position of the substituents on the electrochemical properties of the pyrrole ring have been studied. Using the optimized structures obtained for these molecules and their cations, IR and NMR spectra have been calculated and analyzed. The results of this study, including charge- and spin-density distribution analyses, show that among all of these compounds 3-fluoropyrrole and 3,4-difluoropyrrole have the most suitable conditions for electropolymerization.
Journal of Physics B: Atomic, Molecular and Optical Physics (09534075)37(20)pp. 4143-4157
Ionization of the hydrogen molecular ion under linearly polarized intense laser fields is simulated by direct solution of the fixed-nuclei time-dependent Schrödinger equation for X = 790 nm and 1 = 1 × 1014 W cm-2. Different adaptive grids used in this study produced very similar results. The results are in agreement with, and thus support, the results of recent calculations carried out by other researchers. Detailed structure of the ionization rates is presented which has not been reported so far in the literature. The use of the virtual detector method resulted in more details of the ionization rates of the hydrogen ion molecule and hydrogen atom. This method especially allowed a simultaneous detection of the parallel and perpendicular components of the ionization rates.
Khosravi-darani, K., Sabzyan, H., Zeini-isfahani, A., Parsafar, G.
Iranian Journal Of Chemistry And Chemical Engineering (10219986)23(2)pp. 45-53
In this work, a more accurate prediction of liquid evaporation flux has been achieved. The statistical rate theory approach, which is recently introduced by Ward and Fang and exact estimation of vapor pressure in the layer adjacent to the liquid-vapor interface have been used for prediction of this flux. Firstly, the existence of an equilibrium layer adjacent to the liquid-vapor interface is considered and the vapor pressure in this layer and its thickness calculated. Subsequently, by using the Fick's second law, an appropriate vapor pressure expression for the pressure of equilibrium layer is derived and by this expression and the statistical rate theory approach, evaporation flux is predicted more accurately than the previous work. Finally, some novel steady state evaporations are simulated and the effects of both liquid and vapor temperature and the effect of the length of the evaporation chamber on the evaporation flux are investigated.
Journal of Chemical Physics (10897690)120(9)pp. 4306-4315
Proton nuclear magnetic resonance spin-lattice relaxation time measurements were conducted at 500 MHz proton Larmor frequency on two hydrogen-argon gas mixtures. Relaxation times were also calculated using quantum mechanical close-coupled computations. The differences found between the experimental and theoretical results indicate that the short-range anisotropy of the potential surface is too weak. It was shown that the reciprocal regime possess much higher sensitivity to changes in the anisotropic component of the intermolecular potential energy surface.
JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM (01661280)712(1-3)pp. 109-115
A question has been raised on the possible difference between the two electric polarizability tensor elements perpendicular to the molecular axis of OCS molecule, possibly, due to the significant difference between O=C and C=S pi-bonds, predicted by both the VB and localized MO theories. In other words, the VB and localized MO pictures for this molecule has been criticized. This question has been addressed by examining electronic characteristics as well as the degeneracy of the bending vibrational modes of this molecule at different ab initio RHF, CIS, MP4, and DFT-B3LYP levels of theory. The results showed that no isolated molecular orbitals corresponding to the individual O=C and C=S pi-bonds exist in this molecule. It is also found that electronic characteristics of this molecule have a cylindrical symmetry with respect to the molecular axis, as is expected from the symmetry of its total Hamiltonian reflected in the HF, post-HF and DFT-KS orbitals. Deficiency of classical VB theory is suggested to be cured by introducing a new type of resonance in which different resonance structures differ only in the orientation of the set of atomic valence orbitals, which are correlated by a C-n operation, without any differences in the bond orders and cross-populations between the participating atoms. (C) 2004 Elsevier B.V. All rights reserved.
Physical Review A - Atomic, Molecular, and Optical Physics (10502947)71(6)
Ionization rates of the hydrogen molecular ion H-2(+) under linearly polarized pulse of intense laser fields are simulated by direct solution of the fixed-nuclei time-dependent Schrodinger equation for the Ti:sapphire laser lines lambda=790 and 800 nm at high intensities starting from just above the Coulomb explosion threshold (i.e., 6.0x10(13), 1.0x10(14), 3.2x10(14), and 1.4x10(15) W cm(-2)). Results obtained in this research exhibit a high degree of complexity for the R-dependent enhanced ionization rates for the H-2(+) system in these intense laser fields. The R-dependent ionization peaks move towards small internuclear distances and their structure becomes simpler and smoother with the increase in the intensity of the laser pulse, i.e., with the decrease in the Keldysh parameter. Results obtained in this research are comparable to and even more reliable than the results of other theoretical calculations reported recently and successfully simulate the experimental ionization data.
JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM (01661280)713(1-3)pp. 43-49
Quantum mechanical ab initio and density functional theory methods have been used to describe electrical and thermochemical properties of all fluoropyrroles and their anions and cations. The study of electrical properties was based on the values of orbital energy spacings including HUMO-LUMO gap (HLG) and electronic spatial extent (ESE) calculated at DFT-B3LYP/6-31G** level of theory. Results of this computational study are compatible with the assumptions that electron transport occurs through the lowest unoccupied molecular orbital. and that the conduction barrier is determined by the molecular electrochemical potential. This study also shows that molecules become polarized and eventually charged as the applied external potential increases. Also. thermochemical properties of fluoropymoles have been calculated at room temperature (298.15 K) and at 373.15 K. Preliminary study on some representative fluoropyrroles has been carried out using U/RHF. MP2 and DFT-B3LYP methods with a variety of basis sets. However, only B3LYP/6-31G** calculations gave satisfactory results. Details of the computational techniques and geometry optimization procedures and some other characteristics of these compounds have been reported in [H. Sabzyan, A. Omrani, J. Phys. Chem. A. 107 (2003) 6476]. (C) 2004 Elsevier B.V. All rights reserved.
In response to the preceding Comment, results of our research show that rate is not necessarily linearly time-dependent and it is possible to define and calculate instantaneous ionization rate. We show that a negative ionization rate and the quiver motion in strong laser field are not necessarily correlated and may occur independently. Furthermore, a negative ionization rate is not identical to recombination. Details of the instantaneous ionization rate and photoelectron kinetic energy release are calculated and analyzed for the evolution of the electron wave packet of H-2(+) in a 25-cycle ultrashort intense linearly polarized laser pulse of I=1.0 x 1014 W/cm(2) intensity and lambda=1064 nm wavelength with a sin(2)-shaped envelope.
Indian Journal of Chemistry - Section A Inorganic, Physical, Theoretical and Analytical Chemistry (09750975)47(7)pp. 979-985
Internal energy of liquid methane has been obtained based on the pair-wise additive approximation for the effective pair potential of dense fluids using (12,6) Lennard-Jones model for the intermolecular potential function. This internal energy has been compared with the internal pressure via the equation of state (EoS) expression. Thus, the effective pair potential parameters (EPPP) through some given EoSs for dense fluids have been calculated. A relation between the potential parameters with EoS parameters has been obtained. Using the obtained EPPPs and applying the pair-wise additive approximation, one could calculate accurately the thermodynamics functions such as total energy. The results of such calculations for the total energy of the liquid methane obtained via the EPPPs from different EoSs indicate a good agreement with the experimental data. Physical interpretation for the state dependencies of the obtained EPPPs from given EoSs is also presented.
