First-Principles Phase Stability Calculations of Zr3Al1-xNbx Alloys with L12 and DO a Structures

We reports the effect of substitution of Nb on the physical properties of Zr3Al1-xNbx using the FP-LAPW method based on the density functional theory (DFT) for structural, electronic, and mechanical properties. In order to understand the relative stability between L12 and DOa structures by the gradual substitution of Nb in Zr3Al, we have performed total-energy calculations for Zr3Al0.75Nb0.25, Zr3Al0.5Nb0.5, and Zr3Al0.25Nb0.75 in both L12 and DOa structures at different volumes. The first-principles calculations clearly show that the cubic symmetry, which favors greater ductility, is retained by the alloy up to the composition Zr3Al0.5Nb0.5 and hence may be of potential use for structural applications. The transition from cubic to orthorhombic structure is found to be in good agreement with experimental observation. The cohesive energy, equilibrium lattice constants, and bulk modulus, including its pressure derivative as a function of Nb substitution, are also calculated and compared with the available experimental values.