The crystal structure of Co2P from X-ray powder diffraction data and its mineralogical applications


Authors: Skála R, Drábek M

Published in: Bulletin of Geosciences, volume 76, issue 4; pages: 209 - 216;

Keywords: Co2P, ab initio crystal structure solution from powder data, phosphide, schreibersite, nickelphosphide, florenskyite, meteorites,

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The structure of stoichiometric Co2P was solved ab initiofrom powder diffraction data. We found the Co2P phase to be orthorhombic, space group Pnma. Unit-cell dimensions refined from powder data are a= 5.6479(4), b = 3.5129(2), c = 6.6078(4) Å, V= 131.10(1) Å3, number of formula units in the unit cell Z= 4. All atoms within the structure are located in 4 csites. Phosphorus is nine-coordinated and cobalt atoms are fourand five-coordinated. Structure motifs found in Co2P are very different from those in members of Fe3P-Ni3P solid solution, which may explain the limited miscibility of the title compound in phosphide phases of the schreibersite-nickelphosphide series. Contrary to that, the similarities between the crystal structures of Co2P and members of the Fe2P-Ni2P solid solution invite the interpretation that relatively higher concentrations of Co could be accommodated in barringerite-type phases in meteorites. A complete mutual miscibility can be expected between Co2P and florenskyite (FeTiP)-like phases, which are isotypic.