First-principles study on the thermal expansion of Ni-X binary alloys based on the quasi-harmonic Debye model

Abstract

In this study, we use the quasi-harmonic Debye model to predict the coefficient of thermal expansion of Ni- X binary alloys. The method bridges between the macroscopic elastic behavior and thermodynamic properties of materials without an expensive calculation of the volume dependence of the phonon density of states. Furthermore, the Gruneisen parameter is derived from the volume dependence of the Debye temperature, which is calculated from the first-principles elastic stiffness constants. The experimental coefficient of thermal expansion (CTE) of pure nickel is well reproduced, especially in the low temperature region. Among the few alloying elements tested, Al is predicted to slightly decrease the CTE whereas Mo and W are more effective in reducing the CTE. For the cases of Ni-X binary alloy systems, where the variation in the CTE is relatively small, the method used here appears to perform better than certain other formulations that rely entirely on the energy vs. volume relationship.