Equation of state and high‐pressure stability of Fe 3 P‐schreibersite: Implications for phosphorus storage in planetary cores

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We have collected in situ X‐ray diffraction patterns of end‐member Fe 3 P‐schreibersite in a diamond anvil cell to pressures of 30 GPa at 300 K. Some samples of Fe 3 P were also laser heated at high pressure to temperatures of ∼2000 K and examined following thermal quench. Below 8 GPa, variation of the schreibersite unit cell delineates a smooth pressure‐volume curve corresponding to a second order Birch‐Murnaghan equation of state with bulk modulus, K 0 T , of 159(1) GPa. Above 8 GPa, however, the schreibersite structure shows substantial stiffening, and an unidentified structure develops between 17 and 30 GPa; upon decompression to ambient pressure the schreibersite structure returns. Therefore, although ubiquitous in iron‐rich meteorites, it is unlikely that schreibersite is the stable phosphorus‐bearing phase in deep planetary cores.