The structure, mechanical, electronic and thermodynamic properties of bcc Zr-Nb alloy: A first principles study

Abstract

First principles calculations based on different substitution models are performed to investigate the structural, elastic, thermodynamic, and electronic properties of body-centered cubic (bcc) Zr-Nb alloy which has great potential in biomedicine and nuclear power in the whole interval of concentration. The results show that the calculated lattice parameters decrease linearly with the increase of Nb concentration which are in good accordance with the experimental and other first principles calculations. The structure of bcc Zr is unstable at 0 K, and Nb additions can improve bcc Zr-Nb solid solution mechanical stability. Bcc Zr-Nb disordered solid solution with the relaxed structure deviate from the perfect bcc lattice position and transform into a more stable non-β phase, however, the atoms of the ordered solid solution occupy maintains the ideal sites of bcc structure. The elastic constants Cij, elastic modulus (B, G, E), Poisson’s ratio and elastic anisotropy also have been calculated. When the structure of bcc Zr-Nb alloy is stable, the Nb addition can increase the elastic modulus, B/G ration and Poisson's ratio which will improve the ductility of alloy. The electronic properties have been investigated based on density of states and charge density difference. The bcc Zr-Nb alloy electronic structure is usually composed of metal bonds and covalent bonds, and metal bonds is dominated. Zr50Nb50 has the highest covalent bond ratio. Finally, the thermodynamic properties are evaluated by quasi-Debye model.