论文标题
根据基于Anharmonic Phonon理论的有限温度下的结构优化：应用于Batio $ _3 $的结构相变
Ab initio structural optimization at finite temperatures based on anharmonic phonon theory: Application to the structural phase transitions of BaTiO$_3$
论文作者
论文摘要
我们基于自洽的声子（SCP）理论制定了在有限温度（$ t $）下结构优化的第一原则方案，该理论准确地考虑了强声子非谐调的效果。单位单元格和内部原子构型形状的$ t $依赖性是通过最大程度地减少SCP理论中的变异自由能来确定的。在每个优化步骤中，在不运行其他电子结构计算的情况下计算新结构中的原子质常数，这使该方法显着有效。我们证明了Batio $ _3 $中的硅和三步结构相变的热膨胀及其压力温度（$ p $ - $ t $）的相图。目前的形式主义将为具有复杂结构相图的材料的有限$ t $在有限的$ t $上的非经验预测开辟道路。
We formulate a first-principle scheme for structural optimization at finite temperature ($T$) based on the self-consistent phonon (SCP) theory, which accurately takes into account the effect of strong phonon anharmonicity. The $T$-dependence of the shape of the unit cell and internal atomic configuration is determined by minimizing the variational free energy in the SCP theory. At each optimization step, the interatomic force constants in the new structure are calculated without running additional electronic structure calculations, which makes the method dramatically efficient. We demonstrate that the thermal expansion of silicon and the three-step structural phase transitions in BaTiO$_3$ and its pressure-temperature ($p$-$T$) phase diagram are successfully reproduced. The present formalism will open the way to the non-empirical prediction of physical properties at finite $T$ of materials having a complex structural phase diagram.
