无超胞情况下极化子跳跃输运的最优过渡态
Optimal transition states for polaron hopping transport without supercells
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中文总结 AI 辅助
研究极化子跳跃输运问题，基于变分极化子方程和弦方法构建无超胞框架，直接在倒易空间优化过渡态，应用于LiF和TiO₂揭示跳跃机制，计算的迁移率与实验相符，建立了第一性原理极化子跳跃动力学的可扩展途径。
中文摘要 AI 辅助
极化子的形成使电荷载流子局部化，并促使材料中的输运从类能带转变为跳跃式。跳跃动力学可通过过渡态的密度泛函理论（DFT）超胞计算获得，但存在极化子自相互作用、虚假静电以及与极化子大小的缩放性差等问题。我们基于变分极化子方程和弦方法引入了一个无超胞框架，用于从头算极化子跳跃输运。该方法直接在倒易空间中优化自陷极化子态之间的过渡态，并提供沿路径的极化子构型，从而能够评估绝热跳跃速率和迁移率。我们将该方法应用于LiF和金红石TiO₂，揭示了多步和各向异性的跳跃机制。在金红石TiO₂中，计算得到的电子 - 极化子迁移率与实验结果一致，而类能带玻尔兹曼输运则大幅高估了迁移率。我们的结果为电荷运动受自陷控制的材料中的第一性原理极化子跳跃动力学建立了一条可扩展的途径。
英文摘要
Polaron formation localizes charge carriers and drives a crossover from band-like to hopping transport in materials. Hopping dynamics can be obtained from DFT supercell calculations of transition states, but these suffer from polaron self-interaction, spurious electrostatics, and poor scaling with polaron size. We introduce a supercell-free framework for ab initio polaron hopping transport based on the ab initio polaron equations formalism, its variational formulation, and the string method. The approach optimizes transition states between self-trapped polaron states directly in reciprocal space and provides the polaron configurations along the path, enabling evaluation of adiabatic hopping rates and mobilities. We apply the method to LiF and rutile TiO$_2$, revealing multi-step and anisotropic hopping mechanisms. In rutile TiO$_2$, the computed electron-polaron mobility agrees with experiment, whereas band-like Boltzmann transport substantially overestimates the mobility. Our results establish a scalable route to first-principles polaron-hopping dynamics in materials in which charge motion is governed by self-trapping.
