Molecular modeling of isomorphous substitution of rhodium for tungsten in a scheelite crystal latticeстатья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:The problem of substitution of Rh(VI) for W(VI) was solved through molecular (cluster) modeling with the use of ab initio SCF methods. A fragment of the scheelite unit cell containing five tetrahedral <WO4> fragments and modified with K' ions was used as a model cluster. The type of structure at the point of the potential energy surface minimum was found to completely correspond to the geometry of the initial model cluster. The equilibrium W-O distance in the central tetrahedral <WO4> moiety of the initial Cluster is 1.774 Angstrom against 1.78 Angstrom in scheelite. The correspondence of the optimal geometry of the <[WO4(WO4)(4)]> framework in the model complex to the experimental structure made it possible to study the distortion of the central moiety upon the substitution of Rh for W. Such a substitution was shown to be energetically possible. Some increase in the unit cell volume is prognosticated, which is in agreement with experimental data.