The crystal structure of garnets (I): The residual electron density distribution in pyrope

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Abstract The crystal structure of pyrope, Mg3Al2Si3O12, was refined by the X-ray diffraction method with anharmonic thermal vibration considered, applying the Gram-Charlier series expansion up to the fourth-rank tensors (R = 0.015 for 688 reflexions). A positive electron density residue due to bonding electrons 0.7 eÅ−3 in height was observed between the silicon and oxygen atoms. Crystal data: [Natural specimen from Parigi, Martiniana Po, Cuneo, Italy; Cubic garnet structure; Ia[unk]d; Z = 8; a o = 11.4582(6) Å; V = 1504.35 Å3; Dx = 3.560 g cm−3; μ = 11.88 cm−1; λ(MoKα) = 0.71069 Å, F(000) = 1600; T = 296 K].