The equilibrium structural parameters, thermodynamic properties, elastic constants, and several other related properties of LiMAl₂ (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 LiMAl₂ (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 LiMAl₂ (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_V of LiMAl₂ (M = Rh, Pd, Ir and Pt) increases gradually and almost linearly with increasing pressure. The Debye temperature θ_D as well as the melting point T_m of the aggregate materials are calculated using two different empirical expressions. The obtained values of θ_D are around 499.5 (546.4) K for LiRhAl₂, 478.7 (520.6) K for LiPdAl₂, 411 (451) K for LiIrAl₂, and 417.3 (455.2) K for LiPtAl₂ compound, respectively; while those of T_m are found to be around 1566 (1448) K for LiRhAl₂, 1436 (1316) K for LiPdAl₂, 1650 (1502) K for LiIrAl₂, and 1615 (1489) K for LiPtAl₂, respectively. Our calculated data show that the behavior of the thermodynamic properties with increasing temperatures is monotonic for all our materials of interest.

Graphical abstract

中文翻译：

---

LiAl2X（X = Rh、Pd、Ir 和 Pt）金属间化合物的结构、弹性和热力学性质的第一性原理研究

在框架中采用投影增强波赝势 (PAW) 方法研究了 LiMAl ₂ (M = Rh、Pd、Ir 和 Pt) 三元金属间化合物的平衡结构参数、热力学性质、弹性常数和其他几个相关性质在 Quantum Espresso 代码中实现的密度泛函理论 (DFT)。我们对 LiMAl ₂ (M = Rh、Pd、Ir 和 Pt) 化合物的晶格参数的研究结果与实验结果非常吻合，而我们获得的弹性常数结果通常略高于文献中先前报道的理论结果。我们关于机械稳定性标准的结果表明，所有 LiMAl ₂（M = Rh、Pd、Ir 和 Pt）在平衡时是机械稳定的，而 Zener 各向异性因子和弹性各向异性指数的分析表明，所有这些化合物的弹性性能都具有高度的各向异性。根据 Mukhanov 等人的说法。的 (Philos. Mag. 89:2117, 2009) 模型中，LiMAl _{2 (M = Rh、Pd、Ir 和 Pt) 的维氏硬度}H _V随着压力的增加逐渐增加并且几乎呈线性增加。使用两种不同的经验表达式计算聚集材料的德拜温度θ _D以及熔点T _{m 。对于 LiRhAl 2}，获得的θ _D值约为 499.5 (546.4) K_{，LiPdAl 2}为 478.7 (520.6) K，LiIrAl ₂为411 (451) K ，LiPtAl ₂化合物为 417.3 (455.2) K ；而T _{m的值分别为 LiRhAl 2}的 1566 (1448) K、LiPdAl ₂的 1436 (1316) K、LiIrAl ₂的 1650 (1502) K 和 LiPtAl ₂的 1615 (1489) K。我们的计算数据表明，对于我们所有感兴趣的材料，随着温度升高的热力学性质的行为是单调的。

图形概要