Electronic structure, mechanical and physical properties of Ag alloyed α-Nb₅Si₃: first-principles calculations

Abstract

The effect of Ag additions on the structural, mechanical and thermodynamic properties of α-Nb₅Si₃ is systematically investigated using the first-principles calculations based on density functional theory. The calculated formation enthalpies show that when Nb atoms in α-Nb₅Si₃ are replaced by one and two Ag atoms, Ag atoms prefer Nb⁴(c) sites rather than Nb¹⁶(l)sites. With increasing concentration of Ag atoms, the elastic moduli and theoretical Vickers hardness of the α-(Nb₁_ₓAgₓ)₅Si₃ compounds decrease, while they become more ductile. Ag additions slightly raise the mechanical anisotropies of α-(Nb₁_ₓAgₓ)₅Si₃ compounds and increases the linear thermal expansion coefficients of the α-(Nb₁_ₓAgₓ)₅Si₃ compounds along the c and a axes, with a decrease in the αc/αa ratios. Finally, the anisotropy of acoustic velocities and Debye temperatures for the α-(Nb₁_ₓAgₓ)₅Si₃ compounds were also calculated.