We examined pressure-induced phase transitions in Fe2S based on high-pressure and high-temperature X-ray diffraction measurements in a laser-heated diamond-anvil cell. Fe2S is not stable at ambient pressure but is known to form above 21 GPa with the Fe2P-type (C22) structure. Our experiments demonstrate a novel phase transition in Fe2S from the C22 to C23 phase with the Co2P-type cotunnite structure above ~30 GPa. The experiments also reveal a transformation from the C23 to C37 (Co2Si-type) phase above ~130 GPa. While the C23 and C37 structures exhibit the same crystal-lographic symmetry (orthorhombic Pnma), the coordination number of sulfur increases from nine in C23 to ten in C37. Such a sequence of pressure-induced phase transitions in Fe2S, C22 → C23 → C37, are similar to those of Fe2P, while they are not known in oxides and halogens that often adopt the C23 cotunnite-type structure. The newly found cotunnite-type Fe2S phase could be present in solid iron cores of planets, including Mars.

中文翻译：

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Fe2S的一个cotunnite型新高压相

我们基于激光加热金刚石砧台中的高压和高温 X 射线衍射测量检查了 Fe2S 中压力引起的相变。Fe2S 在环境压力下不稳定，但已知会在 21 GPa 以上形成 Fe2P 型 (C22) 结构。我们的实验证明了 Fe2S 中从 C22 到 C23 相的新相变，具有高于 ~30 GPa 的 Co2P 型煤铜矿结构。实验还揭示了从 C23 到 C37（Co2Si 型）相的转变，高于 ~130 GPa。虽然 C23 和 C37 结构表现出相同的晶体对称性（正交 Pnma），但硫的配位数从 C23 中的 9 增加到 C37 中的 10。Fe2S 中的这种压力诱导相变序列，C22 → C23 → C37，类似于 Fe2P，而它们在通常采用 C23 铜镍矿型结构的氧化物和卤素中并不为人所知。新发现的铅矿型 Fe2S 相可能存在于包括火星在内的行星的固体铁芯中。