Ab-initio calculations of elastic constants and thermodynamic properties of LuAuPb and YAuPb half-heusler compounds

In this work, density functional theory plane-wave pseudo potential method with generalized gradient approximation is used to investigate the elastic, mechanical, phonon and thermodynamic properties of LuAuPb and YAuPb compounds. The physical properties such as elastic constants, bulk modulus, shear modulus, Young's modulus, Poisson's ratio and shear anisotropy factor of both the compounds are calculated. The elastic properties of these compounds reveal that these compounds are mechanically stable. Further, the phonon dispersion curves prove that these compounds are also dynamically stable. The study of shear anisotropic factor gives purely anisotropic nature of these compounds. Pugh's and Frantsevich's ratio shows that both these compounds exhibit ductile nature. The sound velocities and Debye temperature of these compounds are also estimated from elastic constants. Using the slack equation, the lattice thermal conductivity of these compounds is also estimated. At room temperature, LuAuPb attains low thermal conductivity as compared to YAuPb. At 300 K, the calculated values of specific heat capacity per atom at constant volume for LuAuPb and YAuPb compounds are 24.37 Jmol−1 K−1 and 23.95 Jmol−1 K−1 respectively. This is the first quantitative theoretical estimation of these properties.