标题： 银碘化物超离子相中的对称性破缺 显示英文标题

标题： Symmetry Breaking in the Superionic Phase of Silver-Iodide

摘要： 在碘化银的超离子相中，我们观察到一种畸变的四方结构，其特征是阳离子分布的对称性破缺。 该相与众所周知的体心立方相竞争，在每原子仅需几毫电子伏特的能量代价下，具有对称的阳离子分布。 小的能量差异表明，这些竞争结构可能在超离子相变温度附近都具有热可访问性。 我们还发现，银离子的分布取决于低温母多形结构，在我们的模拟中可访问的纳秒时间尺度上，超离子相中仍存在记忆效应。 此外，持续约100纳秒的模拟显示，即使在体心立方相稳定的温度下，向四方晶格结构的显著涨落仍然存在。 我们的结果与许多“异常”的实验观测结果一致，并为碘化银中的“记忆效应”提供了一个分子机制。 显示英文摘要

摘要： In the superionic phase of silver iodide, we observe a distorted tetragonal structure characterized by symmetry breaking in the cation distribution. This phase competes with the well known bcc phase, with a symmetric cation distribution at an energetic cost of only a few meV/atom. The small energy difference suggests that these competing structures may both be thermally accessible near the superionic transition temperature. We also find that the distribution of silver ions depends on the low-temperature parent polymorph, with memory persisting in the superionic phase on the nanosecond time scales accessible in our simulations. Furthermore, simulations on the order 100ns reveal that even at temperatures where the bcc phase is stable, significant fluctuations toward the tetragonal lattice structure remain. Our results are consistent with many "anomalous" experimental observations and offer a molecular mechanism for the "memory effect" in silver iodide.