Electrides are an emerging class of materials with excess electrons localized in interstices and acting as anionic interstitial quasi-atoms (ISQs). The spatial ion–electron separation means that electrides can be treated physically as ionic crystals, and this unusual behavior leads to extraordinary physical and chemical phenomena. Here, a completely different effect in electrides is predicted. By recognizing the long-range Coulomb interactions between matrix atoms and ISQs that are unique in electrides, a nonanalytic correction to the forces exerted on the matrix atoms is proposed. This correction gives rise to a longitudinal acoustic-transverse acoustic splitting in the acoustic branch of lattice phonons near the zone center, similar to the well-known longitudinal optical–transverse optical splitting in the phonon spectra of ionic compounds. The factors that govern this splitting are investigated, with isotropic fcc-Li and anisotropic hP4-Na as the typical examples. It is found that not all electrides can induce a detectable splitting, and criteria are given for this type of splitting. The present prediction unveils the rich phenomena in electrides and could lead to unprecedented applications.

中文翻译：

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驻极体中LA-TA异常分裂的预测

电极是一类新兴的材料，其中多余的电子位于间隙中，并充当阴离子间隙准原子（ISQs）。空间离子与电子的分离意味着被选举者可以在物理上被视为离子晶体，这种不寻常的行为导致了异常的物理和化学现象。在此，预测了对驻极体的完全不同的影响。通过认识到基体原子与ISQ之间独特的长距离库仑相互作用，从而对施加在基体原子上的力进行了非解析校正。这种校正在区域中心附近的晶格声子的声支中产生了纵向声-横向声分裂，这与离子化合物的声子光谱中的众所周知的纵向-横向声分裂相似。以各向同性fcc-Li和各向异性hP4-Na为例，研究了控制这种分裂的因素。发现并非所有的选举者都能诱发可检测的分裂，并且给出了这种分裂的标准。当前的预测揭示了选民中的丰富现象，并可能导致空前的应用。