Structure transitions in silica minerals-a joint atudy of X-ray diffraction and computer simulation

二氧化硅矿物的结构转变——X射线衍射和计算机模拟的联合研究

基本信息

批准号：
07640637
负责人：
KIHARA Kuniaki
金额：
$ 1.47万
依托单位：
Kanazawa University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

This study has been projected to establish the atomic views about the mechanism of structure transition and fluctuation of related physical properties in quartz and its isostructural compounds, by combinatorial application of diffraction and spectroscopic techniques. Although two years were not long enough to perform all the projected subjects, especially spectroscopic experiments, several powerful computer programs were developed to analyze position-time data provided by usual molecular dynamics calculations.Detailed crystal structure analyzes of AlPO_4 and GaPO_4, both having the quartz type structures, were also completed for single crystal intensity data obtained at different temperatures.The software package CRYSTAL has five program-units, SDSTR, MDPDF, ORDERP, DTRANS and NOMODE, each executed by teading in data from MD calculations, to calculate scattering intensities (for neutron or X-ray diffraction), dynamical structure factors, atomic probability density functions, atomic mean-square displacements, order parameters and finally normal mode analysis (still under development), respectively. In application of these programs to the MD results for berlinite AlPO_4, an order-disorder type mechanism was found to play important role in the alpha-betastructure transition in this mineral. This result is so important and still preliminary at present, but is not consistent with recent studies such as X-ray results (by the present author), hyper Raman results and hard mode infrared absorption results and so on. The results of the MD calculations must be examined for their reliability, and then some long-term calculations for MD are currently undertaken.

这项研究计划通过衍射和光谱技术的组合应用，建立关于石英及其同构化合物的结构转变和相关物理性质波动机制的原子观点。虽然两年的时间不足以完成所有计划的课题，特别是光谱实验，但开发了几个强大的计算机程序来分析通常的分子动力学计算提供的位置-时间数据。AlPO_4和GaPO_4的详细晶体结构分析，两者都具有石英类型结构，还完成了在不同温度下获得的单晶强度数据。软件包 CRYSTAL 有 5 个程序单元：SDSTR、MDPDF、ORDERP、DTRANS 和 NOMODE，每个程序单元都通过导入 MD 计算的数据来执行，分别计算散射强度（对于中子或 X 射线衍射）、动力学结构因子、原子概率密度函数、原子均方位移、阶次参数以及最终的简正模分析（仍在开发中）。在将这些程序应用于柏林石AlPO_4的MD结果时，发现有序-无序类型机制在该矿物的α-β结构转变中发挥重要作用。这个结果非常重要，目前仍处于初步阶段，但与最近的研究如X射线结果（作者的）、超拉曼结果和硬模式红外吸收结果等并不一致。必须检查 MD 计算结果的可靠性，然后目前正在进行一些 MD 的长期计算。