Computing binary alloy phase diagrams with explicit configurational and vibrational entropy
Abstract
Phase stability in multicomponent solid solutions depends on configurational entropy beyond the ideal mixing limit, but capturing it together with vibrational entropy within the same atomistic framework remains challenging. Here, we extend non-equilibrium thermodynamic integration to composition-dependent transformations through an alchemical interpolation of the interactions, combined with Monte Carlo identity exchange moves and molecular dynamics that sample the vibrational and non-ideal configurational entropy along the integration path. We apply the framework to the Au-Cu binary alloy using Atomic Cluster Expansion (ACE) potentials trained on density functional theory data using the LDA, PBE, and r2SCAN functionals, and construct composition-temperature phase diagrams directly from atomistic free energies. We find that explicit configurational sampling lowers the AuCu order-disorder transition temperature predicted by an ACE potential trained on LDA data by about 126 K, closer to the experimental value of 683 K, and substantially widens the stability range of the solid solution. At the same time, the much larger sensitivity to the exchange-correlation functional shows that this level of agreement should not be interpreted as general predictive accuracy. No single functional is uniformly accurate across the thermodynamic observables considered here, showing that functional sensitivity must be assessed alongside configurational effects when constructing atomistic phase diagrams.
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BibTeX
@misc{menon2026computing,
title = {{Computing binary alloy phase diagrams with explicit configurational and vibrational entropy}},
author = {Sarath Menon and Marvin Poul and Tilmann Hickel and Jörg Neugebauer and Ralf Drautz},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2607.14795},
eprint = {2607.14795},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.14795},
}
RIS
TY - UNPB
TI - Computing binary alloy phase diagrams with explicit configurational and vibrational entropy
AU - Sarath Menon
AU - Marvin Poul
AU - Tilmann Hickel
AU - Jörg Neugebauer
AU - Ralf Drautz
PY - 2026
DA - 2026/10/29
PB - arXiv
DO - 10.48550/arxiv.2607.14795
UR - https://arxiv.org/abs/2607.14795
AB - Phase stability in multicomponent solid solutions depends on configurational entropy beyond the ideal mixing limit, but capturing it together with vibrational entropy within the same atomistic framework remains challenging. Here, we extend non-equilibrium thermodynamic integration to composition-dependent transformations through an alchemical interpolation of the interactions, combined with Monte Carlo identity exchange moves and molecular dynamics that sample the vibrational and non-ideal configurational entropy along the integration path. We apply the framework to the Au-Cu binary alloy using Atomic Cluster Expansion (ACE) potentials trained on density functional theory data using the LDA, PBE, and r2SCAN functionals, and construct composition-temperature phase diagrams directly from atomistic free energies. We find that explicit configurational sampling lowers the AuCu order-disorder transition temperature predicted by an ACE potential trained on LDA data by about 126 K, closer to the experimental value of 683 K, and substantially widens the stability range of the solid solution. At the same time, the much larger sensitivity to the exchange-correlation functional shows that this level of agreement should not be interpreted as general predictive accuracy. No single functional is uniformly accurate across the thermodynamic observables considered here, showing that functional sensitivity must be assessed alongside configurational effects when constructing atomistic phase diagrams.
ER -