Electronic structure, elastic behavior, and stability of Pressure-Responsive Lithium-Based Intermetallics: A study of Li2PdX (X = Ga, Ge, In), Li2InPt, Li2InAu, and LiPd3

Abstract

The structural, electronic, mechanical properties, and phonon dispersions of lithium-based intermetallic compounds Li2PdX (X = Ga, Ge, In), Li2InPt, Li2InAu, and LiPd3 are investigated using density functional theory (DFT) via the Wien2k code. Stability is analyzed through energy-volume curves, cohesive and formation energies, elastic tensor components, and phonon density of states. Hydrostatic pressure effects on stability and mechanical properties are also examined. The results confirm the stability of these compounds in nonmagnetic cubic phases, with calculated lattice parameters and bulk moduli in agreement with existing data, validating the computational approach. Phonon density of states analysis establishes the dynamical stability of Li2PdGa and Li2PdGe in space group Fm3¯m (No. 225); Li2InPt, Li2InAu, and Li2PdIn in F4¯3m (No. 216); and LiPd3 in Pm3¯m (No. 221). Elastic properties reveal a critical pressure point (Pt) beyond which mechanical instability occurs. Around Pt, Pugh's ratio (bulk-to-shear modulus ratio) exhibits limiting behavior, persisting as long as C44 is comparable to C11-C12. However, for LiPd3, a marked reduction in C44 near Pt eliminates this behavior, underscoring its distinct mechanical response. A derived limit for Pugh's ratio offers new insights into the elastic behavior of these materials under extreme conditions. Electronic properties, including the density of states and linear electronic specific heat coefficient, confirm the metallic nature of these compounds. These findings provide valuable insights into the pressure-dependent mechanical and electronic behavior of lithium-based intermetallic compounds, informing their potential applications in energy storage, electronic devices, and pressure-sensing. © 2025