Interstitial Carbon in bcc HfNbTiVZr high entropy alloy from first principles

TL;DR

This study uses density functional theory to analyze how dilute carbon atoms behave as interstitials in bcc HfNbTiVZr high entropy alloy, revealing complex long-range effects on its structure.

Contribution

First-principles calculations reveal the instability of tetrahedral carbon interstitials and complex long-range interactions in bcc HfNbTiVZr high entropy alloy.

Findings

Carbon interstitials in tetrahedral sites are unstable.

Large structural relaxations occur due to interstitials.

Long-range effects influence solution energetics.

Abstract

The remarkable mechanical properties of high entropy alloys can be further improved by interstitial alloying. In this work we employ density functional theory calculations to study the solution energies of dilute carbon interstitial atoms in tetrahedral and octahedral sites in bcc HfNbTiVZr. Our results indicate that carbon interstitials in tetrahedral sites are unstable, and the preferred octahedral sites present a large spread in the energy of solution. The inclusion of carbon interstitials induces large structural relaxations with long-range effects. The effect of local chemical environment on the energy of solution is investigated by performing a local cluster expansion including studies of its correlation with the carbon atomic Voronoi volume. However, the spread in solution energetics can not be explained with a local environment analysis only pointing towards a complex, long-range influence of interstitial carbon in this alloy.