Structural, mechanical, thermodynamic and electronic properties of AgIn2 and Ag3In intermetallic compounds: ab initio investigation

Abstract

The structural, mechanical, thermodynamic and electronic properties of two Ag–In phase crystals, i.e., AgIn₂ and Ag₃In intermetallic compounds (IMCs), are explored using ab initio calculations within the generalized gradient approximation. The optimized lattice constants of AgIn₂ and Ag₃In crystals are first investigated in the study. Next, the elastic constants of the two single crystal structures as well as their associated polycrystalline elastic properties, such as bulk modulus, Young's modulus, shear modulus and Poisson's ratio, are predicted through Voigt–Reuss–Hill approximation. The mechanical characteristics of these two crystals, such as ductile–brittle characteristic and elastic anisotropy, are further assessed by way of the calculation of the Cauchy pressures, Zener anisotropy factor and directional Young's modulus. Additionally, the temperature-dependence of Debye temperature and heat capacity are obtained according to a quasi-harmonic Debye model, and their band structures and density of states profiles are evaluated through analysis of electronic characteristics. The calculation results show that these two IMC crystals are not only an elastically anisotropic, low stiff and very ductile material but also a conductor. The elastic anisotropy, mechanical property, Debye temperature and heat capacity of Ag₃In all surpass those of AgIn₂, and also, Ag₃In tends to be much stiffer than AgIn₂. Furthermore, the heat capacity of these two crystals strictly follows with the well-known T³-law at temperature below the Debye temperature and would reach the Dulong–Petit limit at temperature above the Debye temperature.