Structural Evolution of Schreibersite, Fe3P, at High Pressure

Fe3P schreibersite is an abundant mineral in iron meteorites. Previous work [Scott et. al., Geophys. Res. Lett. (2007) 34, L06302/1-5] reported a phase transition occurred in a powder sample of Fe3P schreibersite above 17 GPa at ambient temperature, but did not identify the structure of this high pressure phase. This high pressure phase is not quenchable to ambient pressure, however, the transition and its reversion may induce characteristic twinning in schreibersite crystals, which may be identified in meteoritic material and, thus, help to constrain shock pressures for iron meteorites. By using a diamond anvil cell with a methanol/ethanol pressure medium to generate pressure, the structure of single crystal Fe3P was studied by X-ray diffraction up to 30 GPa (at room temperature) at end station 16 ID-B of the Advanced Photon Source. Our experiment indicates that the phase transition occurs around 10 GPa and appears to suggest that the material twins during compression. Acknowledgement: The authors thank the HPCAT team for their help, and U.S. DOE Cooperative Agreement No. FC08-06NA27684 with UNLV for supporting the work. Portions of this work were performed at HPCAT (Sector 16), APS, ANL. HPCAT facility is supported by DOE-BES, DOE-NNSA, NSF, and the W.M. Keck Foundation. The APS is supported by the U. S. DOE-BES under Contract No. W-31-109-Eng-38.