DFT Study of Au3In and Au3In2 Intermetallic Compounds: Structural Stability, Fracture Toughness, Anisotropic Elasticity, and Thermophysical Properties for Advanced Applications

This study systematically explores the structural stability, mechanical properties, elastic anisotropy, fracture toughness, and thermophysical characteristics of Au3In and Au3In2 intermetallic compounds (IMCs) through density functional theory (DFT) simulations. Employing the generalized gradient approximation (GGA) and the Voigt–Reuss–Hill approximation enables precise predictions of polycrystalline elastic behavior, providing critical insights into the intrinsic stability and mechanical anisotropy of these IMCs. Structural optimization identifies the equilibrium lattice parameters and cohesive energies, indicating stronger atomic bonding and superior structural stability in Au3In relative to Au3In2. Elastic constant calculations confirm mechanical stability and reveal pronounced anisotropic elastic behavior; Au3In exhibits significant stiffness along the [010] crystallographic direction, while Au3In2 demonstrates notable stiffness predominantly along the [001] direction. Both Au3In and Au3In2 exhibit ductile characteristics, confirmed by positive Cauchy pressures and elevated bulk-to-shear modulus (K/G) ratios. Fracture toughness analysis further establishes that Au3In offers greater resistance to crack propagation compared to Au3In2, suggesting its suitability in mechanically demanding applications. Thermophysical property evaluations demonstrate that Au3In possesses higher thermal conductivity, elevated Debye temperature, and superior volumetric heat capacity relative to Au3In2, reflecting its enhanced capability for effective thermal management in electronic packaging. Anisotropy assessments, utilizing both universal and Zener anisotropy indices, reveal significantly higher mechanical anisotropy in Au3In2, influencing its practical applicability.