A First-Principles Study of the Structural, Mechanical and Thermodynamic Properties of Ag-In IMCs

In this work, four mechanically stable Ag-In intermetallic compounds (AgIn
2
, α'-Ag
3
In, ζ-Ag
3
In and γ-Ag
9
In
4
) have been selected to explore their crystal structures, elastic mechanical and thermodynamic properties by first-principles calculations. Predicting the average mechanical properties of polycrystal based on the calculated elastic constants of single crystals, it can be learned that the Young's modulus of AgIn2,
$\alpha^{\prime}-\text{Ag}_{3}\text{In}, \zeta-\text{Ag}_{3}\text{In}$
and
$\gamma-\text{Ag}_{9}\mathbf{In}_{4}$
were 62.464 GPa, 96.281 GPa, 80.590 GPa, 80.169 GPa, respectively, and showed anisotropic distributions along with the shear modulus. Among them, α‘- Ag
3
In and γ-Ag
9
In
4
have isotropic bulk modulus. They both have low hardness, and good ductility which can enhance the ability to resist external impacts and improve the reliability of microelectronic packages. Predictions of their heat capacities show that the heat capacities all follow T3 law at low temperatures and converge to the Dulong-Petit limit.