论文标题
研究超级离子材料中离子扩散，热传输和热运动的分子动力学模拟中的有限尺寸效应
Investigating finite-size effects in molecular dynamics simulations of ion diffusion, heat transport, and thermal motion in superionic materials
论文作者
论文摘要
研究了模拟框的有限大小在平衡分子动力学模拟中的影响，用于不同类型的典型超级公式导体，即氟含石结构材料PBF2，CAF2和UO2和UO2（类型-II）以及AGI的α相（I型I）。经过大量验证的经验力场被用来运行NS长的模拟，并提取几种属性的一般趋势，以增加大小和较宽的温度范围。这项工作表明，对于被考虑的II型超电部导体，扩散率很大程度上取决于系统的大小，并且超级离子状态转移到较小的细胞中的较大温度。此外，只有几百个原子的模拟才能捕获实验观察到的传播过程的激活能量的特征变化，该传播过程发生在阶阶转变为超级离子机制下。在α-AGI中，对离子扩散的有限大小影响要弱得多。对于较小的细胞，通常在温度明显较低的温度下达到温度独立的（Allen-Feldman）状态的较小细胞，通常发现热导率。对组成固体基质的非移动离子的热运动的有限尺寸影响遵循固体的简单定律。
The effects of the finite size of the simulation box in equilibrium molecular dynamics simulations are investigated for prototypical superionic conductors of different types, namely the fluorite-structure materials PbF2, CaF2, and UO2 (type-II), and the α phase of AgI (type I). Largely validated empirical force-fields are employed to run ns-long simulations and extract general trends for several properties, at increasing size and in a wide temperature range. This work shows that, for the considered type-II superionic conductors, the diffusivity dramatically depends on the system size and that the superionic regime is shifted to larger temperatures in smaller cells. Furthermore, only simulations of several hundred atoms are able to capture the experimentally-observed, characteristic change in the activation energy of the diffusion process, occurring at the order-disorder transition to the superionic regime. Finite-size effects on ion diffusion are instead much weaker in α-AgI. The thermal conductivity is found generally smaller for smaller cells, where the temperature-independent (Allen-Feldman) regime is also reached at significantly lower temperatures. The finite-size effects on the thermal motion of the non-mobile ions composing the solid matrix follow the simple law which holds for solids.
