Ab initio study of the relative stability under pressure of MgSiO3-ilmenite, -perovskite, and (periclase + stishovite)

The study of mantellic phases is challenging the experimentalist. Experimental difficulties emphasize the importance of theoretical approaches which should provide not only good calculated geometries, but also consistent sets of. thermochemical data. Two high-pressure polymorphs of MgSiO3 adopt the ilmenite (I/) and perovskite ( Pv) structures. We present the first ab initio study of the relative stability of these two polymorphs, and of the assemblage MgO-periclase (Pe)+stishovite (St) as a function of pressure.