Dynamical structure analyses of phase transitions and physical properties in minerals

本研究结合声子频率的晶格动力学计算，解释了一些常见矿物，如石英及其相关材料的精确结构分析中获得的X射线衍射数据。主要研究结果总结如下：1。在正常结构分析中得到的石英中原子的各向异性德拜-沃勒因子在晶格动力学计算中得到了充分的重现。这一协议有力地支持了阿尔法-贝塔相变是相当替代的2。以前在α-β相变附近发现的石英原子的德拜-沃勒因子的尖点状反常，不仅是由光学软模引起的，也是由00xi方向的低频声学模引起的。具有石英型结构的AlPO_4的α-β相变也发生了位移。衍射数据，如原子的各向异性温度因子，可以与晶格动力学计算相结合，成为分析结构动力学的有用候选数据。

In this study, X-ray diffraction data obtained in accurate structure analyses of some common minerals such as quartz and its related materials were interpreted in conjunction with lattice dynamical calculations of phonon frequencies. The chief results are summarized below.1. Anisotropic Debye-Waller factors of atoms in quartz obtained in normal structure analyses were reproduced in lattice dynamical calculations with sufficient agreement. This agreement strongly supports that the alpha-beta phase transition is rather displacive.2. The cusp-shape anomaly of the Debye-Waller factors of atoms in quartz, which were previously found around the alpha-beta transition, was found to be caused not only by the optic soft mode, but also by the low frequency acoustic mode in the 00xi direction.3. The alpha-beta transition in AlPO_4, which has the quartz-type structure, is also displacive.4. Diffraction data such as anisotropic temperature factors of atoms can be a useful candidate in analyzing dynamics of structures, in conjunction with lattice dynamical calculations.