Water Phase Diagram from a General-Purpose Atomic Cluster Expansion Potential

Fuente: arXiv
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Autores principales: Ibrahim, Eslam, Lysogorskiy, Yury, Drautz, Ralf, Piaggi, Pablo
Formato: Preprint
Publicado: 2026
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author Ibrahim, Eslam
Lysogorskiy, Yury
Drautz, Ralf
Piaggi, Pablo
author_facet Ibrahim, Eslam
Lysogorskiy, Yury
Drautz, Ralf
Piaggi, Pablo
contents Water's phase diagram remains one of the most intricate and challenging benchmarks in molecular modeling. In this study, we compute the phase diagram of water using an Atomic Cluster Expansion (ACE) potential trained on density-functional theory (DFT) calculations based on the revPBE-D3 exchange and correlation functional. We compute solid-liquid chemical potential differences and melting points using biased coexistence simulations with the On-the-Fly Probability Enhanced Sampling (OPES) method. Starting from these points, we trace coexistence lines using Gibbs-Duhem integration. This combination of methods allows us to consistently map pressure-temperature phase boundaries and reconstruct the full phase diagram between approximately 100-500 K and 0-4 GPa. The stability regions of the main ice polymorphs (Ih, II, V, VI, and VII) are reproduced in close agreement with experiments. As in earlier studies based on DFT, ice III is metastable and there are systematic shifts of coexistence lines with respect to experimental results. Our results demonstrate the capability of our general-purpose ACE potential to capture the complex phase behavior of water across wide thermodynamic conditions.
format Preprint
id arxiv_https___arxiv_org_abs_2601_12947
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Water Phase Diagram from a General-Purpose Atomic Cluster Expansion Potential
Ibrahim, Eslam
Lysogorskiy, Yury
Drautz, Ralf
Piaggi, Pablo
Materials Science
Water's phase diagram remains one of the most intricate and challenging benchmarks in molecular modeling. In this study, we compute the phase diagram of water using an Atomic Cluster Expansion (ACE) potential trained on density-functional theory (DFT) calculations based on the revPBE-D3 exchange and correlation functional. We compute solid-liquid chemical potential differences and melting points using biased coexistence simulations with the On-the-Fly Probability Enhanced Sampling (OPES) method. Starting from these points, we trace coexistence lines using Gibbs-Duhem integration. This combination of methods allows us to consistently map pressure-temperature phase boundaries and reconstruct the full phase diagram between approximately 100-500 K and 0-4 GPa. The stability regions of the main ice polymorphs (Ih, II, V, VI, and VII) are reproduced in close agreement with experiments. As in earlier studies based on DFT, ice III is metastable and there are systematic shifts of coexistence lines with respect to experimental results. Our results demonstrate the capability of our general-purpose ACE potential to capture the complex phase behavior of water across wide thermodynamic conditions.
title Water Phase Diagram from a General-Purpose Atomic Cluster Expansion Potential
topic Materials Science
url https://arxiv.org/abs/2601.12947