Solubility in Zr-Nb alloys from first-principles

TL;DR

This study uses first-principles calculations to analyze the thermodynamic properties and phase diagram of Zr-Nb alloys, emphasizing the importance of vibrational free energy contributions for accurate modeling.

Contribution

It provides a detailed ab initio analysis of Zr-Nb alloy solubility, highlighting the role of atomic vibrations in phase stability and improving phase diagram predictions.

Findings

Solution energies agree with experimental data

Vibrational free energy significantly affects phase stability

Accurate phase diagram description requires vibrational contributions

Abstract

The thermodynamic properties of the Zr-Nb alloy are investigated at temperatures below 890 K with ab initio calculations. The solution energies of the bcc Nb-rich and hcp Zr-rich solid solutions obtained within the framework of density functional theory are in good agreement with experimental data, although insufficient for a quantitative description of the miscibility gap, for which non configurational entropy has to be accounted for. Whereas electronic free energies can be neglected, we show, using the harmonic approximation and the density functional perturbation theory, that both solution free energies are strongly modified by the contribution related to atomic vibrations. Considering this vibrational free energy leads to a good description of the phase diagram.