Towards Quantum Geophysics: Quantum Deductive Molecular Mechanics of high- and low-pressure silica polymorphs.


A.L. Tchougreeff


A.N. Frumkin Institute of Physical Chemistry & Electrochemistry of RAS



Abstract:

Previously we developed (quantum) Deductive Molecular Mechanical (DMM) [1-3] models of some fundamental elements (stoicheia) of ancients, namely, fire [4] – actually, of C2 occurring in flames, and water [5,6] of which we considered solid water phases — ices. Furthemore, we applied similar ideas to carbon allotropes [7-9] Now, we switch to analogous consideration of the prinicipal component of upper and middle Earth crust — silica (SiO2). Two boundary cases of seifertite/stishovite featuring the octahedral coordination of the Si atoms by sp2 oxygen atoms and of tridimite/cristobalite featuring the tetrahedral coordination of the Si atoms by sp3 oxygens are compared within the analytical approach [1-3] and the boundary between them in the P-T phase diagram is reproduced with a reasonable precision within a very simple physically sensible model.

Rerefences

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