解耦固体电解质中的阳离子–聚阴离子耦合：哪种阴离子运动主导阳离子输运？
Disentangling Cation-Polyanion Coupling in Solid Electrolytes: Which Anion Motion Dominates Cation Transport?
AI总结：
本文结合约束算法与机器学习分子动力学，解耦聚阴离子平移、旋转和振动对锂/钠固体电解质阳离子迁移的影响，发现三类运动均可驱动超离子性且主导模式随频率和材料类别变化。
摘要：
锂和钠固体电解质具有聚阴离子骨架和高迁移率阳离子。理解并量化聚阴离子动力学对阳离子的影响，将有助于揭示阴离子在超离子导体中所起的复杂作用。然而，目前没有任何实验或计算方法能够直接提取这一信息，因为聚阴离子动力学总是与其他影响离子迁移率的因素相耦合。在这里，我们提出了一项开创性研究，将约束算法与机器学习分子动力学相结合，在多种材料类别中定量揭示聚阴离子的平移、旋转和振动对阳离子迁移率的影响。通过对每种阴离子运动模式施加选择性约束的超长时间、大规模机器学习分子动力学模拟，明确得到了近室温及高温条件下的结果。与以往认为容易发生的阴离子旋转主要促进阳离子输运的理解形成鲜明对比，本研究首次揭示了阴离子平移和振动与阳离子扩散之间的强耦合；我们发现平移、旋转和振动各自都能直接驱动超离子性，并且在每一类材料中通常有一种运动占主导地位。当旋转频率与阳离子跳跃频率匹配时，阴离子旋转主导阳离子输运；而在较高旋转频率下阴离子平移占优势，在较低旋转频率下则是振动占优势。阴离子动力学对阳离子扩散的影响在较低温度下变得更加显著。
英文摘要：
Lithium and sodium solid electrolytes feature polyanion frameworks and highly mobile cations. Understanding and quantifying the impact of polyanion dynamics on cations will help us to unravel the complex role that anion play in superionic conductors. However, no experimental or computational method can directly extract this information, as polyanion dynamics are always coupled with other factors that affect ion mobility. Here, we present the pioneering study that combines constraint algorithm and machine-learning molecular dynamics to quantitatively reveal the effects of polyanion translation, rotation, and vibration on cation mobility across a diverse material class. Ultralong-time, large-scale machine-learning molecular dynamics simulations with selective constraints on each anion motion mode unequivocally yield results at near room and elevated temperatures. In sharp contrast to the previous understanding that facile anion rotation primarily facilitates cation transport, the strong coupling between anion translation and vibration with cation diffusion has been unraveled for the first time; we find that translation, rotation, and vibration can each directly drive superionicity, with one typically dominant in each class of materials. Anion rotation dominates cation transport when the rotation frequency matches the cation hopping frequency, whereas anion translation prevails at higher and vibration at lower rotation frequencies. The impact of anion dynamics on cation diffusion becomes more prominent at lower temperatures.
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