X-ray Single-crystal Diffraction Study of Pyrope In the Temperature-range 30-973 K

X-ray single-crystal diffraction data are presented for synthetic pyrope garnet over the temperature range 30-973 K, which extends the range previously studied. The structure refinements allow a detailed geometrical analysis of the polyhedral distortions over this temperature range, the determination of the thermal expansion for bond distances, and the determination of atomic displacement parameters. The problem of static or dynamic disorder of the Mg site is discussed on the basis of the temperature behavior of the atomic displacement tensors, which show no evidence of static disorder on this site. The high-temperature anharmonic contribution to the thermal vibrations is investigated by the use of Gram-Charlier high-order expansion terms of the displacement parameter tenser