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: 5447106
• 负责人: Professor Dr. Björn Winkler
• 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/5447106?language=en
• 关键词: Thermodynamics; mixing; ordering; solid; solutions

The chemical variability of many rock-forming minerals - solid solutions, is determined bythe coupled-substitution mechanism. This mechanism permits a cation to enter the lattice of ahost 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 ofcationic order both at inermediate and at the end-member compositions. Static lattice energycalculations (SLEC) and Monte Carlo simulations are the only tools which permit relatisticmodeling of these phase. The success of this approach is determined by the quality of theempirical interatomic potentials used to constrain the SLEC. We propose to make the use ofan 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 goodperformance in predicting magnitudes of the mixing and ordering enthalpy in a variety ofminerals and industrially important compounds. The main outcomes of the project will be thedevelopment of realistic activity-composition models for solid solutions with coupledsubstitutions such as CaMg, = (Na,K)(Al, Fe3+) in clinopyroxene, Mg,Si=Al,Al inclinopyroxene and perovskite, (Na,K)Si=CaAl ind feldspar and Si,Zr4+=P5+, Y3+ in zircon.

许多造岩矿物--固溶体的化学可变性是由偶合取代机制决定的。这种机制允许阳离子进入主体矿物的晶格，即使它的电荷与特定位置的平均电荷不匹配。由于中间体和端元组成的阳离子有序的发展，这种固溶体的热力学行为是复杂的。静态晶格能计算(SLEC)和蒙特卡罗模拟是唯一允许对这些相进行关联建模的工具。这种方法的成功与否取决于用于约束SLEC的经验原子间势的质量。我们建议利用已建立的Si4+，Al3+，Mg2+，Ca2+，Na+，K+，Fe2+，Fe3+，Mn2+，Ti4+，ZR4+，Y3+，P5+，O2-体系的自洽原子间相互作用势集来预测各种矿物和工业上重要的化合物的混合和有序热的大小。该项目的主要成果将是开发具有偶联取代的固溶体的实际活性-组成模型，例如单斜辉石、镁、硅=铝、斜方辉石和钙钛矿中的CaMG=(Na，K)(Al，Fe3+)，(Na，K)Si=CaAl ind长石和锆石中的Si，Zr4+=P5+，Y3+。