Efficient method for calculation of low-temperature phase boundaries

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Hauptverfasser: Svensson, Lucas, Sadigh, Babak, Wu, Christine, Erhart, Paul
Format: Preprint
Veröffentlicht: 2026
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author Svensson, Lucas
Sadigh, Babak
Wu, Christine
Erhart, Paul
author_facet Svensson, Lucas
Sadigh, Babak
Wu, Christine
Erhart, Paul
contents Understanding phase stability and phase transformations is central to predicting material behavior under varying thermodynamic conditions. One of the earliest and most influential applications of density functional theory in materials science has been the prediction of pressure-induced phase transitions at 0 K. Extending these calculations to finite temperatures, however, requires accounting for thermal, quantum, and anharmonic contributions to the free energy, often at significant computational cost. In this work, we present a general and efficient framework for calculating low-temperature phase boundaries by combining the Clausius-Clapeyron equation with the quasi-harmonic approximation. This methodology requires a minimal number of calculations, while naturally incorporating internal degrees of freedom as well as quantum and low-order anharmonic effects. We illustrate the accuracy and efficiency of the approach by constructing the phase diagram of silica in the pressure range from -2 to 12 GPa and temperatures up to 1750 K. To this end, we employ a machine-learned interatomic potential trained on density functional theory reference data, enabling well-converged free energy estimates via efficient thermodynamic sampling and a rigorous comparison between the proposed framework and free energy integration.
format Preprint
id arxiv_https___arxiv_org_abs_2603_09804
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Efficient method for calculation of low-temperature phase boundaries
Svensson, Lucas
Sadigh, Babak
Wu, Christine
Erhart, Paul
Materials Science
Chemical Physics
Computational Physics
Understanding phase stability and phase transformations is central to predicting material behavior under varying thermodynamic conditions. One of the earliest and most influential applications of density functional theory in materials science has been the prediction of pressure-induced phase transitions at 0 K. Extending these calculations to finite temperatures, however, requires accounting for thermal, quantum, and anharmonic contributions to the free energy, often at significant computational cost. In this work, we present a general and efficient framework for calculating low-temperature phase boundaries by combining the Clausius-Clapeyron equation with the quasi-harmonic approximation. This methodology requires a minimal number of calculations, while naturally incorporating internal degrees of freedom as well as quantum and low-order anharmonic effects. We illustrate the accuracy and efficiency of the approach by constructing the phase diagram of silica in the pressure range from -2 to 12 GPa and temperatures up to 1750 K. To this end, we employ a machine-learned interatomic potential trained on density functional theory reference data, enabling well-converged free energy estimates via efficient thermodynamic sampling and a rigorous comparison between the proposed framework and free energy integration.
title Efficient method for calculation of low-temperature phase boundaries
topic Materials Science
Chemical Physics
Computational Physics
url https://arxiv.org/abs/2603.09804