Database analysis and crystal structural prediction applied to mica minerals

What is it about?

The existence of some 450 crystal structural refinements of mica minerals allows a generalized, computerized analysis of the subtle structural changes that occur with varying pressure, temperature or chemical composition (p-T-X). This analysis is embedded in the Microsoft Excel Solver, enabling prediction of the crystal structural parameters of micas under p-T-X conditions that have not been experimentally investigated.

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Photo by Raphaël Biscaldi on Unsplash

Photo by Raphaël Biscaldi on Unsplash

Why is it important?

Several innovations in the modelling of mineral crystal structures are presented: 1). At the core is a transformation of minimally distorted (Si,Al)O4 tetrahedra into equivalent pseudocubes, whose form is completely defined by up to six parameters. This is a significant advance and simplification in quantitative crystal chemistry. 2). The database-led modelling requires the use of versatile generators for the AO12, MO4(OH)2 and TO4 polyhedra. 3). The modelling techniques are presented in the Microsoft EXCEL framework. Their exploitation of VBA and the Solver allows the prediction of crystal structures under p-T-X conditions deviating from known experimental work. The method can also be incorporated into systematic structural refinements. 4). The EXCEL-VBA programs are made available via a weblink, allowing users to use or adapt these for their own work.

Perspectives