Abstract
Application of the Debye model to the temperature dependence of atomic mean square displacements determined by X-ray diffraction provides individual knowledge of dynamic and static natures of atomic displacements, together with characteristic values of crystals such as Debye temperature and one particle potential coefficients. The anharmonic refinement, incorporating the higher-order terms into the Debye-Waller factor, is a useful technique to detect the deformation of the probability density functions from ellipsoidal distribution due to anharmonic thermal vibrations and static disorders of atoms. Here we review our recent research that applied these approaches to Mg3Al2Si3O12 garnet, an important constituent in the Earth's interior. The research has proved the presence of the Mg static disorder, which has long been a controversial issue, and has proposed the possibility of anharmonic thermal vibrations of atoms at high temperature.
