Thermodynamics of mixing and ordering in solid solutions with coupled substitutions: A computer simulation approach

耦合取代固溶体中混合和排序的热力学：计算机模拟方法

• 批准号: 5447102
• 负责人: Professor Dr. Andrew Putnis
• 金额: --
• 依托单位: Fachrichtung Mineralogie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2005
• 资助国家: 德国
• 起止时间: 2004-12-31 至 2006-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/5447102?language=en
• 关键词: Thermodynamics; mixing; ordering; solid; solutions

The chemical variability of many rock-forming minerals - solid solutions, is determined by the coupled-substitution mechanism. This mechanism permits a cation to enter the lattice of a host mineral even when its charge does not match the average charge of the particular site. The termodynamic behaviour of such solid solutions is complicated due to the development of cationic order both at inermediate and at the end-member compositions. Static lattice energy calculations (SLEC) and Monte Carlo simulations are the only tools which permit relatistic modeling of these phase. The success of this approach is determined by the quality of the empirical interatomic potentials used to constrain the SLEC. We propose to make the use of an already developed self-consistent set of interatomic potentials for the system Si4+, Al3+, Mg2+, Ca2+, Na+, K+, Fe2+, Fe3+, Mn2+, Ti4+, ZR4+, Y3+, P5+, O2-, which shows good performance in predicting magnitudes of the mixing and ordering enthalpy in a variety of minerals and industrially important compounds. The main outcomes of the project will be the development of realistic activity-composition models for solid solutions with coupled substitutions such as CaMg, = (Na,K)(Al, Fe3+) in clinopyroxene, Mg,Si=Al,Al in clinopyroxene and perovskite, (Na,K)Si=CaAl ind feldspar and Si,Zr4+=P5+, Y3+ in zircon.

许多造岩矿物固溶体的化学变异性是由耦合取代机制决定的。这种机制允许阳离子进入主体矿物的晶格，即使其电荷与特定位置的平均电荷不匹配。这种固溶体的热力学行为是复杂的，由于在中间体和端员组合物的阳离子顺序的发展。静态晶格能计算（SLEC）和蒙特卡罗模拟是唯一的工具，允许这些阶段的相对论建模。这种方法的成功取决于用于约束SLEC的经验原子间势的质量。我们建议利用已经开发的一套自洽的原子间相互作用势的系统Si 4+，Al 3+，Mg 2+，Ca 2+，Na+，K+，Fe 2+，Fe 3+，Mn 2+，Ti 4+，Zr 4+，Y 3+，P5+，O2-，这在预测各种矿物和工业上重要的化合物的混合和有序焓的大小表现出良好的性能。该项目的主要成果将是为具有耦合替代的固溶体开发现实的活性-组成模型，例如单斜辉石中的CaMg =（Na，K）（Al，Fe 3+），单斜辉石和钙钛矿中的Mg，Si=Al，Al，长石中的（Na，K）Si=CaAl，锆石中的Si，Zr 4 +=P5+，Y3+。