Electronic structure, phase stability, and transport properties of the AlTiVCr lightweight high-entropy alloy: A computational study

TL;DR

This computational study explores the atomic structure, phase stability, and electronic transport of the AlTiVCr high-entropy alloy, revealing temperature-dependent chemical ordering and its effects on resistivity.

Contribution

It predicts a high-temperature B2 chemical ordering and its impact on electronic properties, providing new insights into the alloy's atomic-scale structure and behavior.

Findings

B2 chemical ordering emerges at high temperatures

Residual resistivity increases with chemical ordering

Ground state is a fully ordered, low-resistivity structure

Abstract

We investigate the thermodynamics and phase stability of the AlTiVCr lightweight high-entropy alloy using a combination of ab initio electronic structure calculations, a concentration wave analysis, and atomistic Monte Carlo simulations. In alignment both with experimental data and with results obtained using other computational approaches, we predict a $\textrm{B2}$ (CsCl) chemical ordering emerging in this alloy at comparatively high temperatures, which is driven by Al and Ti moving to separate sublattices, while V and Cr express weaker site preferences. The impact of this $\textrm{B2}$ chemical ordering on the electronic transport properties of the alloy is investigated within a Kubo-Greenwood linear response framework and it is found that, counter-intuitively, the alloy's residual resistivity increases as the material transitions from the $\textrm{A2}$ (disordered bcc) phase to our predicted $\textrm{B2}$ (partially) ordered structure. This is understood to result primarily from a reduction in the density of electronic states at the Fermi level induced by the chemical ordering. At low temperatures, our atomistic Monte Carlo simulations then reveal subsequent sublattice orderings, with the ground-state configuration predicted to be a fully-ordered, single-phase structure with vanishing associated residual resistivity. These results give fresh, insight into the atomic-scale structure and consequent physical properties of this well-studied, technologically relevant material.