Synthesis and structure of olivine-like arsenates LiMAsO4LiMAsO4 (M=MnM=Mn, Fe, Co and Ni) and their high-pressure spinel-like polymorphs

High pressure has been applied to olivine-like arsenates (LiMAsO4LiMAsO4; M=Mn, Fe, Co and Ni), some of them being reported for the first time, to transform them to the corresponding spinel-like polymorph. Below the limit of our experimental set-up (8 GPa, 1273 K) the well known olivine-spinel transformation occurred for all investigated cases but for the manganese one. This transformation is observed for the first time in arsenates and the title compounds are the first examples of arsenic-containing spinel-like oxides. The structure of the olivine and spinel polymorphs are reported.

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