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

The effect of Ag additions on the structural, mechanical and thermodynamic properties of alpha-Nb5Si3 is systematically investigated using the first-principles calculations based on density functional theory. The calculated formation enthalpies show that when Nb atoms in alpha-Nb5Si3 are replaced by one and two Ag atoms, Ag atoms prefer Nb-4c sites rather than Nb-161 sites. With increasing concentration of Ag atoms, the elastic moduli and theoretical Vickers hardness of the alpha-(Nb1-xAgx)(5)Si-3 compounds decrease, while they become more ductile. Ag additions slightly raise the mechanical anisotropies of alpha-(Nb1-xAgx)(5)Si-3 compounds and increases the linear thermal expansion coefficients of the alpha-(Nb1-xAgx)(5)Si-3 compounds along the c and a axes, with a decrease in the alpha(c)/alpha(a) ratios. Finally, the anisotropy of acoustic velocities and Debye temperatures for the alpha-(Nb1-xAgx)(5)Si-3 compounds were also calculated.