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arXiv 2110.07883cond-mat.mtrl-sci
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热力学滞后的定量预测：Pd-H相变的温度依赖性

Quantitative predictions of thermodynamic hysteresis: Temperature-dependent character of the phase transition in Pd-H

J. Magnus Rahm, Joakim Löfgren, Paul Erhart

备注：
11 pages, 6 figures
发表信息：
Acta Materialia 227, 117697 (2022)
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摘要：

尺寸不匹配但共格的相之间的相变热力学不同于传统的无应力热力学。最值得注意的是，在开放系统中，这种相变总是与滞后相关联。尽管实验证据的相关性，这些影响在技术上重要的材料，如钯氢化物，配方的第一性原理为基础的原子尺度建模的相干，开放系统一直缺乏。在这里，我们开发了一种方法，用于量化相边界，滞后，和相干界面自由能使用密度泛函理论，合金簇展开，和蒙特卡罗模拟在一个约束合奏。我们将这种方法应用于Pd-H，并表明相变在大约400 K以上改变特征，在任何时候都发生空间均匀的氢浓度，即，两相不共存。我们的研究结果与实验观察是一致的，但揭示了在实验中尚未访问的Pd纳米粒子中的氢化物形成的方面。

英文摘要：

The thermodynamics of phase transitions between phases that are size-mismatched but coherent differs from conventional stress-free thermodynamics. Most notably, in open systems such phase transitions are always associated with hysteresis. In spite of experimental evidence for the relevance of these effects in technologically important materials such as Pd hydride, a recipe for first-principles-based atomic-scale modeling of coherent, open systems has been lacking. Here, we develop a methodology for quantifying phase boundaries, hysteresis, and coherent interface free energies using density-functional theory, alloy cluster expansions, and Monte Carlo simulations in a constrained ensemble. We apply this approach to Pd--H and show that the phase transition changes character above approximately 400 K, occurring with an at all times spatially homogeneous hydrogen concentration, i.e., without coexistence between the two phases. Our results are consistent with experimental observations but reveal aspects of hydride formation in Pd nanoparticles that have not yet been accessible in experiment.

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