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


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.


  1. A.L. Tchougréeff. SO(4) Group and Deductive Molecular Mechanics. J. Mol. Struct. THEOCHEM, 630 (2003) 243-263. doi:10.1016/S0166-1280(03)00163-5.
  2. A.L. Tchougréeff, A.M. Tokmachev. Deductive Molecular Mechanics of sp3 Carbon Atom. Int. J. Quant. Chem., 96 (2004) 175-184.
  3. A.L. Tchougréeff, A.M. Tokmachev. Deductive Molecular Mechanics of sp3 Nitrogen Atom and Its Application to Analysis of a QM/MM Interface. Int. J. Quant. Chem., 100 (2004) 667-676.
  4. A.L. Tchougréeff, R. Dronskowski. Two Theorems about C2 and Some More. Mol. Phys., 114 (2016) № 7-8, 1423-1444 doi: 10.1080/00268976.2016.1158422.
  5. A.L. Tchougréeff. Περὶ του στοιχειου του υδατος or Deductive Molecular Mechanics of Crystalline Water. AIP Conf. Proc., 1906 (2017) 030004 doi: 10.1063/1.5012283.
  6. A.L. Tchougréeff. De glaciēbus or Deductive Molecular Mechanics of Ice Polymorphs. Theor. Chem. Acc., 137 (2018) 138 doi: 10.1007/s00214-018-2322-0.
  7. I.V. Popov, A.L. Görne, A.L. Tchougréeff, R. Dronskowski. Relative stability of diamond and graphite as seen through bonds and hybridizations. Phys. Chem. Chem. Phys., 21 (2019) 10961 - 10969 doi: 10.1039/c8cp07592a.
  8. I.V. Popov, V.V. Slavin, A.L. Tchougréeff, R. Dronskowski. Deductive molecular mechanics of four-coordinated carbon allotropes. Phys. Chem. Chem. Phys., 21 (2019) 18138 - 18148 doi: 10.1039/C9CP03504D.
  9. И.В. Попов, А.Л. Чугреев, Р. Дронсковски. Дедуктивная молекулярная механика аллотропов углерода. Физ. Низк. Темп./Low Temp. Phys. 46 (2020) № 7, 781-798 [in Russian]/ 655 (2020) doi: 10.1063/10.0001361 [in English].