Reliable First-Principles Alloy Thermodynamics via Truncated Cluster Expansions

TL;DR

This paper introduces an optimal truncation method for cluster expansions in alloy thermodynamics, improving reliability and predictive power in first-principles calculations, exemplified by Ni3V.

Contribution

The authors develop a well-defined truncation procedure for cluster expansions that guarantees reliable thermodynamic predictions, addressing previous failures in alloy modeling.

Findings

Achieved agreement with experimental data for Ni3V

Predicted new low-energy alloy structures

Identified causes of prior cluster expansion failures

Abstract

In alloys cluster expansions (CE) are increasingly used to combine first-principles electronic-structure and Monte Carlo methods to predict thermodynamic properties. As a basis-set expansion in terms of lattice geometrical clusters and effective cluster interactions, the CE is exact if infinite, but is tractable only if truncated. Yet until now a truncation procedure was not well-defined and did not guarantee a reliable truncated CE. We present an optimal truncation procedure for CE basis sets that provides reliable thermodynamics. We then exemplify its importance in Ni$_3$V, where the CE has failed unpredictably, and now show agreement to a range of measured values, predict new low-energy structures, and explain the cause of previous failures.