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.

预计这项研究是通过结合衍射和光谱技术的结合应用，建立了关于石英及其同生成化合物中相关物理特性机理的原子观点。尽管两年的时间不足以执行所有预期的受试者，尤其是光谱实验，但开发了几个强大的计算机程序来分析由通常的分子动力学计算提供的位置时间数据。alpo_4和Gapo_4的详细级晶体结构分析，既有Quartz型结构，均已完成了Quartz类型结构，还可以在不同的晶体强度数据中获得五个晶体强度数据。 MDPDF，Orderp，dtrans和Nomode通过在MD计算中捕捉数据来计算散射强度（用于中子或X射线衍射），动态结构因子，原子概率密度函数，原子均值平均值，订单参数和最终正常模式（仍在开发下）。在将这些程序应用于Berlinite Alpo_4的MD结果时，发现在该矿物的Alpha-Betrstructure Transition中，发现了订单disorder类型机制。该结果是如此重要，目前仍然是初步的，但与最近的研究（如本作者），超拉曼结果和硬模式红外吸收结果等最新研究不一致。必须检查MD计算结果的可靠性，然后目前进行一些MD的长期计算。