First principles study of structural, elastic, and thermodynamic properties of LiAl.sub.2X

• Published in: The European physical journal. B, Condensed matter physics Vol. 95; no. 7
• Main Authors: Benamrani, Ammar, Daoud, Salah, Bouarissa, Nadir
• Format: Journal Article
• Language: English
• Published: Springer 01.07.2022
• Subjects: Analysis; Anisotropy; Density functionals; Intermetallic compounds; Palladium; Thermodynamics
• ISSN: 1434-6028
• DOI: 10.1140/epjb/s10051-022-00370-5

The equilibrium structural parameters, thermodynamic properties, elastic constants, and several other related properties of LiMAl.sub.2 (M = Rh, Pd, Ir and Pt) ternary intermetallic compounds have been investigated, employing the projected augmented wave pseudopotentials (PAW) approach in the framework of the density functional theory (DFT) as implemented in the Quantum Espresso code. Our findings on the lattice parameters of LiMAl.sub.2 (M = Rh, Pd, Ir and Pt) compounds agree well with the experimental ones, while our obtained results of the elastic constants are in general slightly higher than the theoretical ones reported previously in literature. Our results concerning the mechanical stability criteria indicate that all LiMAl.sub.2 (M = Rh, Pd, Ir and Pt) are mechanically stable at equilibrium, while the analyses of both Zener anisotropy factor and elastic anisotropy index show that all these compounds are highly anisotropic in their elastic properties. According to Mukhanov et al.'s (Philos. Mag. 89:2117, 2009) model, the Vickers hardness H.sub.V of LiMAl.sub.2 (M = Rh, Pd, Ir and Pt) increases gradually and almost linearly with increasing pressure. The Debye temperature [theta].sub.D as well as the melting point T.sub.m of the aggregate materials are calculated using two different empirical expressions. The obtained values of [theta].sub.D are around 499.5 (546.4) K for LiRhAl.sub.2, 478.7 (520.6) K for LiPdAl.sub.2, 411 (451) K for LiIrAl.sub.2, and 417.3 (455.2) K for LiPtAl.sub.2 compound, respectively; while those of T.sub.m are found to be around 1566 (1448) K for LiRhAl.sub.2, 1436 (1316) K for LiPdAl.sub.2, 1650 (1502) K for LiIrAl.sub.2, and 1615 (1489) K for LiPtAl.sub.2, respectively. Our calculated data show that the behavior of the thermodynamic properties with increasing temperatures is monotonic for all our materials of interest.