Thermodynamics of solid solutions based on first-principles simulations of supercells of host phases with defects of the solute component

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The project outlines two novel approaches to modelling of the excess and the standard thermodynamic properties of geochemically and petrologically important solid solutions. The Double Defect Method (DDM) considers isostructural solutions, i.e. systems formed by end-members, which belong to the same space group, e.g. calcite-magnesite. The Single Defect Method (SDM), deals with non-isostructural systems, e.g. the solid solution of CaSO4 in calcite. While the DDM is concerned with concentrated solid solutions and is able to describe effects of short and long-range order, the SDM is applicable to diluted solid solutions, and is able to predict concentrations of a virtual (trace) component dispersed within the host phase. Both approaches are based on first-principles simulations of supercell structures of host phases with single or paired defects of the solute. Research areas, which will benefit from the proposed developments include trace-element geothermometry, i.e. the thermometry based on the distribution of trace elements between rock-forming minerals; geoecology, e.g. the prediction of retention levels of hazardous elements in rock-forming minerals; high-pressure mineralogy, e.g. the estimation of thermodynamic properties of pressure-stabilized end-members; materials science, e.g. the prediction of phase diagrams of ceramics systems, which include solid solutions.