High pressure is able to modify profoundly the chemical bonding and generate new phase structures of materials with chemical and physical properties not accessible at ambient conditions. We here report an unprecedented phenomenon on the pressure-induced formation of semiconducting electrides via compression of layered alkaline-earth subnitrides Ca₂N, Sr₂N, and Ba₂N that are conducting electrides with loosely confined electrons in the interlayer voids at ambient pressure. Our extensive first-principles swarm structure searches identified the high-pressure semiconducting electride phases of a tetragonal I4̅2d structure for Ca₂N and a monoclinic Cc structure shared by Sr₂N and Ba₂N, both of which contain atomic-size cavities with paring electrons distributed within. These electride structures are validated by the excellent agreement between the simulated X-ray diffraction patterns and the experimental data available. We attribute the emergence of the semiconducting electride phases to the p–d hybridization on alkaline-earth-metal atoms under compression as well as the filling of the p–d hybridized band due to the interaction between Ca and N. Our work provides a unique example of pressure-induced metal-to-semiconductor transition in compound materials and reveals unambiguously the electron-confinement topology change between different types of electrides.

中文翻译：

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碱土金属亚氮化物中的压力稳定型半导体

高压能够深刻地改变化学键合，并产生具有在环境条件下无法获得的化学和物理特性的材料新的相结构。我们在这里报告了一种前所未有的现象，即在环境压力下，通过层状碱土金属氮化物Ca ₂ N，Sr ₂ N和Ba ₂ N的压力诱导形成的半导体氮化物的形成，所述层状氮化物以疏松约束电子的形式导电于层间空隙中。我们广泛第一原理群结构检索鉴定高压半导体四方的电子化合物相余42 d结构的Ca ₂ N和单斜抄送由Sr ₂ N和Ba ₂ N共享的结构，它们都包含原子大小的腔体，内部分布着成对的电子。通过模拟的X射线衍射图和可用的实验数据之间的出色一致性，验证了这些电子结构。我们认为所述半导体电子化合物相到p的出现-上碱土金属原子d杂交下压缩，以及作为p的填充- d杂交带由于Ca和N.我们的工作之间的相互作用提供了一个独特的复合材料中压力诱导的金属到半导体跃迁的例子，清楚地揭示了不同类型的电子之间的电子约束拓扑变化。