Ab initio investigation of the intermetallics in the Nb-Sn binary system

The elastic and thermodynamic properties of the stable intermetallics in the Nb-Sn system were studied by the first-principles pseudo-potential plane-wave method based on density functional theory. The elastic constants, Debye temperatures, bulk, shear and Young's moduli and Poisson's ratios were calculated for all the phases. Nb3Sn has the highest bulk, shear and elastic moduli of the Nb-Sn intermetallics. The elastic properties at 0 K and the Debye temperatures of the Nb6Sn5 and NbSn2 phases are reported for the first time. The enthalpies of formation were calculated for all the intermetallics. The finite-temperature elastic properties of the Nb and Nb3Sn were calculated using the quasi-static approximation. The thermal expansion coefficients of Nb and Nb3Sn were also obtained.