Superionics是迷人的材料,显示固体和液体样的特征:作为固体,它们对剪切应力有弹性反应;作为液体,它们在正常条件下显示快速离子扩散。除了这样的科学兴趣,优势与能源技术相关,电子,和传感应用。表征和理解它们的弹性特性是,例如,迫切需要解决它们作为全固态电池中固态电解质的可行性。然而,静态弹性方法假设定义良好的参考位置,原子围绕该位置振动,与快速离子导体中移动离子的准液体运动相反。这里,我们从等压-等温系综中的系综波动推导出了超离子的弹性张量,利用广泛的Car-Parrinello模拟。我们将这种方法应用于范式锂离子导体,并用块分析来计算统计误差。在轨迹上采样的静态方法通常会高估响应,强调动态处理在确定超离子弹性张量中的重要性。
Superionics are fascinating materials displaying both solid- and liquid-like characteristics: as solids, they respond elastically to shear stress; as liquids, they display fast-ion diffusion at normal conditions. In addition to such scientific interest, superionics are technologically relevant for energy, electronics, and sensing applications. Characterizing and understanding their elastic properties is, e.g., urgently needed to address their feasibility as solid-state electrolytes in all-solid-state batteries. However, static approaches to elasticity assume well-defined reference positions around which atoms vibrate, in contrast with the quasi-liquid motion of the mobile ions in fast ionic conductors. Here, we derive the elastic tensors of superionics from ensemble fluctuations in the isobaric-isothermal ensemble, exploiting extensive Car-Parrinello simulations. We apply this approach to paradigmatic Li-ion conductors, and complement with a block analysis to compute statistical errors. Static approaches sampled over the trajectories often overestimate the response, highlighting the importance of a dynamical treatment in determining elastic tensors in superionics.