Abstract We found a new phase transition in Fe2P from Co2P-type (C23) to Co2Si-type (C37) structure above 42 ± 2 GPa based on in situ X-ray diffraction experiments. While these two structures have identical crystallographic symmetry, the orthorhombic unit cell is shortened in a-axis but elongated in c-axis, the coordination number of phosphorous increases from nine to 10, and the volume reduces by 2% across the phase transition. The new C37-type Fe2P phase has been found to be stable, at least to 83 GPa at high temperature. The Birch-Murnaghan equation of state for C37 Fe2P was also obtained from pressure-volume data, suggesting that phosphorous contributes to 17% of the observed density deficit of the Earth’s outer core when it includes the maximum 1.8 wt% P as observed in iron meteorites. In addition, since both Fe2S and Ni2Si are also known to have the C37 structure under high pressure, (Fe,Ni)2(S,Si,P) could have wide solid solution and constitute planetary iron cores, although it is not dense enough to be a main constituent of the Earth’s inner core.

中文翻译：

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新的压力诱导相变到 Co2Si 型 Fe2P

摘要 基于原位 X 射线衍射实验，我们在 42 ± 2 GPa 以上发现了 Fe2P 从 Co2P 型 (C23) 到 Co2Si 型 (C37) 结构的新相变。虽然这两种结构具有相同的晶体学对称性，但正交晶胞在 a 轴上缩短但在 c 轴上拉长，磷的配位数从 9 增加到 10，并且在相变过程中体积减少了 2%。已发现新的 C37 型 Fe2P 相是稳定的，在高温下至少达到 83 GPa。C37 Fe2P 的 Birch-Murnaghan 状态方程也是从压力-体积数据中获得的，这表明当它包括在铁陨石中观察到的最大 1.8 wt% 的 P 时，磷对地球外核的观察到的密度缺陷有 17% 的贡献. 此外，