First-principles prediction of ductility in β-type Ti-Mo binary alloys

Recent studies suggest that the ratio of the shear modulus (G) to the bulk modulus (B) and the Poisson's ratio (ν) are good indicators of ductility. Using the method of supercell and the first-principles pseudopotential plane-wave method, the G/B and ν of the β-type Ti-Mo binary alloys with Mo molar fraction (x _Mo) ranging from 6.25% to 37.5% are calculated. The results show that the ductility of β-type Ti-Mo binary alloys first increases with increasing x _Mo and reaches the maximum when x _Mo is about 25%, and then reduces with more increasing x _Mo. The charge density difference calculations suggest that the x _Mo dependence of the ductility can be ascribed to the change of bonding characteristics between Ti and Mo atoms in the [111] direction.