The Earth as a multiscale quantum-mechanical system - 10/12/14
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Abstract |
Major features of the Earth's structure and dynamics originate in the contrast between the rigidity of Si-O bonds and the softness of Si-O-Si linkages. Because this contrast results from orbital hybridization, a real understanding of bonding relies on ab initio quantum-mechanical principles. As investigated with first-principles interatomic potentials, the α–β transitions of SiO2 polymorphs illustrate how soft Si-O-Si linkages give rise to dynamical structures at rather low temperatures and yield the low melting temperatures of SiO2-rich minerals that are at the roots of SiO2 enrichment in magmatic differentiation. The increasing concentration of alkalis throughout this process is another aspect that must also be studied in terms of molecular orbitals in relation with the presence of aluminum in tetrahedral coordination. Finally, calculations of noble gas solubility show that some important features can be treated with “hybrid” calculations when, in addition to quantum-mechanical effects, the energy needed to create a cavity in the silicate melt is dealt with in a classical manner.
Le texte complet de cet article est disponible en PDF.Keywords : Magmatic differentiation, ab initio calculations, SiO2 polymorphs, Silicon-oxygen bonding, Aluminum charge compensation, Noble gas solubility
Plan
Vol 346 - N° 11-12
P. 317-325 - novembre 2014 Retour au numéroBienvenue sur EM-consulte, la référence des professionnels de santé.
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