First principles modeling of mechanical properties of binary alloys containing Ga, Sn, and In for soldering applications.

Using density functional theory, the elastic properties of various binary Ga, Sn and In-based alloys have been calculated to determine their viability as potential replacements for toxic Pb-based solders. Computed quantities such as the bulk K , shear G , and Young's E moduli were used to evaluate the mechanical behavior of the studied materials. The Pugh ratio γ and Poisson's ratio ν were utilized to quantify the ductility of the alloys. Through comparative charge density analysis, we illustrated the relationship between the relative charge distributions and the aforementioned ductility metrics. Among the 52 studied alloys, 27 were determined to be stable/metastable at room temperature, and each of these stable/metastable materials are expected to be ductile. To facilitate the discovery and implementation of thermodynamically accessible and ductile solders, this work focuses on the mechanical properties of the alloys expected to be stable/metastable. Based on the cutoff criteria for stability and ductility established at the end of this work (E Form < 10 meV/atom and γ > 4.00), the α-Ga 0.125 In 0.875 , GaII 0.750 In 0.250 , GaII 0.833 Sn 0.167 and In 0.875 Ga 0.125 alloys warrant further study for soldering applications.