Recent work on superionic conductors has demonstrated the influence of lattice dynamics and the softness of the lattice on ionic transport. When examining either the changes in the acoustic phonon spectrum or the whole phonon density of states, both a decreasing activation barrier of migration and a decreasing entropy of migration have been observed, highlighting that the paradigm of "the softer the lattice, the better" does not always hold true. However, both approaches to monitor the changing lattice dynamics probe different frequency ranges of the phonon spectrum, and thus, it is unclear if they are complementary. In this work, we investigate the lattice dynamics of the superionic conductor Na3PS4- xSe x by probing the optical phonon modes and the acoustic phonon modes, as well as the phonon density of states via inelastic neutron scattering. Notably, Raman spectroscopy shows the evolution of multiple local symmetry reduced polyhedral species, which likely affect the local diffusion pathways. Meanwhile, density functional theory and the ionic transport data are used to compare the different approaches for assessing the lattice dynamics. This work shows that, while acoustic and inelastic methods may be used to experimentally assess the overall changing lattice stiffness, calculations of the average vibrational energies between the mobile ions and the anion framework are important to assess and computationally screen for ionic conductors.

中文翻译：

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使用超离子导体 Na3PS4-xSex 比较用于研究晶格动力学对离子传输影响的描述符

最近关于超离子导体的工作已经证明了晶格动力学和晶格软度对离子传输的影响。在检查声学声子谱的变化或整个声子态密度时，都观察到迁移的激活障碍和迁移熵的减小，突出表明“晶格越软越好”的范式并不总是如此。然而，这两种监测晶格动力学变化的方法都探测声子谱的不同频率范围，因此，尚不清楚它们是否互补。在这项工作中，我们通过探测光学声子模式和声学声子模式来研究超离子导体 Na3PS4-xSe x 的晶格动力学，以及通过非弹性中子散射的声子态密度。值得注意的是，拉曼光谱显示了多个局部对称性减少的多面体物种的演变，这可能会影响局部扩散途径。同时，密度泛函理论和离子输运数据用于比较评估晶格动力学的不同方法。这项工作表明，虽然声学和非弹性方法可用于实验评估整体变化的晶格刚度，但移动离子和阴离子框架之间的平均振动能的计算对于评估和计算筛选离子导体很重要。密度泛函理论和离子传输数据用于比较评估晶格动力学的不同方法。这项工作表明，虽然声学和非弹性方法可用于实验评估整体变化的晶格刚度，但移动离子和阴离子框架之间的平均振动能的计算对于评估和计算筛选离子导体很重要。密度泛函理论和离子传输数据用于比较评估晶格动力学的不同方法。这项工作表明，虽然声学和非弹性方法可用于实验评估整体变化的晶格刚度，但移动离子和阴离子框架之间的平均振动能的计算对于评估和计算筛选离子导体很重要。