Effects of alloying element Ti on α-Nb5Si3 and Nb3Al from first principles

Abstract

The energies and electronic structures of the alloying element Ti in the Nb–Si–Al–Ti three-phase alloy, Nbss (Nb solid solution), Nb5Si3 and Nb3Al, have been studied by the first-principles pseudopotential plane-wave method based on density functional theory. It is found that the preferred sites for the alloying element Ti are the Nb I sublattice sites of α-Nb5Si3 and then the Nb sublattice sites of Nb3Al phase according to the calculations of impurity formation energies. Using a sum of overlap populations of all bonds in the conventional cell, we evaluate the covalent bonding of intermetallic compounds quantitatively. It is found that Ti can decrease the covalent bonding of α-Nb5Si3 and Nb3Al. We also analyse the bond characters using valence charge densities and total density of states.