The diffusion of Li in bulk Si and crystalline LiSi is investigated over a wide range of temperatures employing first-principles calculations based on density functional theory, transition state theory, and the kinetic Monte Carlo method. Nuclear quantum effects are incorporated by computing the vibrational spectrum and its effect on the effective energy barrier. The Li diffusion coefficient in bulk Si calculated with such quantum effects is ∼33% lower than the classical limit near room temperature due to higher effective energy barrier and tends to the classical limit at a high temperature (>1000 K). The presence of anharmonicity, estimated by the quasiharmonic approximation and the cBΩ model, increases the diffusion coefficient by ∼60%. For Li diffusion in LiSi with multiple vacancy jumps, we obtain an effective diffusion barrier of 0.27 eV ± 0.01 eV. In the Li–Si system, the quantum mechanical effects are only marginally significant at room temperature.

中文翻译：

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Li在Si和LiSi中的扩散：核量子效应和非谐性。

利用基于密度泛函理论，过渡态理论和动力学蒙特卡洛方法的第一性原理计算，研究了Li在块状Si和结晶LiSi中的扩散情况。通过计算振动谱及其对有效能垒的影响，可以合并核量子效应。由于较高的有效能垒，通过这种量子效应计算出的块状Si中的Li扩散系数比室温附近的经典极限低约33％，并且在高温（> 1000 K）下趋于经典极限。通过拟谐波近似和cB估计存在非谐波Ω模型，扩散系数增加约60％。对于具有多个空位跃迁的LiSi中的Li扩散，我们获得了0.27 eV±0.01 eV的有效扩散势垒。在锂硅系统中，量子力学效应在室温下仅微不足道。