Breakdown of the Arrhenius Law in Describing Vacancy Formation Energies: The Importance of Local Anharmonicity Revealed by Ab initio Thermodynamics
Breakdown of the Arrhenius Law in Describing Vacancy Formation Energies: The Importance of Local Anharmonicity Revealed by Ab initio Thermodynamics
复制标题
DOI：
10.1103/physrevx.4.011018
复制
发表时间：
2014-02-10
影响因子：
12.5
通讯作者：
Neugebauer, J.
中科院分区：
文献类型：
--
作者：
Glensk, A.;Grabowski, B.;Neugebauer, J.
我们研究了 Al 和 Cu 中从 T = 0 K 到熔化温度期间空位形成吉布斯能的温度依赖性，并充分考虑了非简谐贡献。我们的结果表明，空位的形成熵并不像通常假设的那样恒定，而是几乎随温度线性增加。由此产生的吉布斯形成能的高度非线性温度依赖性自然地解释了正电子湮灭能谱和微分膨胀测量数据之间的差异，并表明非线性热校正对于将高温实验数据外推至T = 0 K至关重要。采用这些校正（而不是分析实验数据时通常假设的线性阿伦尼乌斯外推法），获得了修正后的形成热函，与之前接受的形成热函相差高达20%。使用修正后的实验形成能，我们发现 DFT-GGA 和未修正的实验空位形成能之间的大部分差异消失了。先前接受的 T = 0 K 形成焓与新修订的 T = 0 K 形成焓之间的实质性转变也会对实验基准从头计算方法产生严重后果，例如。例如，导出超出常用 LDA 和 GGA 交换相关泛函（例如 AM05 泛函）的修正。
We study the temperature dependence of the Gibbs energy of vacancy formation in Al and Cu from T = 0 K up to the melting temperature, fully taking into account anharmonic contributions. Our results show that the formation entropy of vacancies is not constant as often assumed but increases almost linearly with temperature. The resulting highly nonlinear temperature dependence in the Gibbs formation energy naturally explains the differences between positron annihilation spectroscopy and differential dilatometry data and shows that nonlinear thermal corrections are crucial to extrapolate high-temperature experimental data to T = 0 K. Employing these corrections-rather than the linear Arrhenius extrapolation that is commonly assumed in analyzing experimental data-revised formation enthalpies are obtained that differ up to 20% from the previously accepted ones. Using the revised experimental formation enthalpies, we show that a large part of the discrepancies between DFT-GGA and unrevised experimental vacancy formation energies disappears. The substantial shift between previously accepted and the newly revised T = 0 K formation enthalpies also has severe consequences in benchmarking ab initio methods against experiments, e. g., in deriving corrections that go beyond commonly used LDA and GGA exchange-correlation functionals such as the AM05 functional.