Accurate and precise thermodynamic models of oxide compounds and their phases are important for calculating the phase stability of oxide materials. We develop and use a coupled quantum mechanical and molecular dynamics approach to create thermodynamic models of hafnia (HfO₂) polymorphs from 0 K to 3000 K at ambient pressure. The approach is based on the quasi-harmonic approximation below the Debye temperature and on ab-initio molecular dynamics calculations above the Debye temperature to predict constant pressure heat capacities (C_p). A Bayesian model provides interpolated values between these regimes. As a case study, we develop thermodynamic models of monoclinic and tetragonal HfO₂ polymorphs. The predicted heat capacities are in excellent agreement with experiment, and the predicted temperature of the monoclinic to tetragonal phase transition (2173 K) is in good agreement with the experimental value (2078K). These results provide a comprehensive and accurate thermodynamic model of the monoclinic and tetragonal phases of hafnia on a broad range of temperatures and can serve as input to CALPHAD assessment of multi-component hafnia-based phase diagrams.

氧化物化合物及其相的准确和精确的热力学模型对于计算氧化物材料的相稳定性很重要。我们开发并使用耦合的量子力学和分子动力学方法来创建在环境压力下从0 K到3000 K的Hafnia（HfO ₂）多晶型物的热力学模型。该方法基于Debye温度以下的准谐波近似和Debye温度以上的从头算分子动力学计算来预测恒压热容量（C _p）。贝叶斯模型提供了这些状态之间的内插值。作为案例研究，我们开发了单斜和四方HfO _2的热力学模型多态。预测的热容量与实验非常吻合，单斜相向四方相变的预测温度（2173 K）与实验值（2078K）非常吻合。这些结果为宽范围内的氧化range的单斜相和四方相提供了全面而准确的热力学模型，可作为CALPHAD评估多组分基于氧化f的相图的输入。