On local structural changes in lizardite-1T: {Si4+/Al3+}, {Si4+/Fe3+}, [Mg2+/Al3+], [Mg2+/Fe3+] substitutions |
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Authors: | Eva Scholtzová ?ubomír Smr?ok |
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Institution: | (1) Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, SK-845 36 Bratislava, Slovak Republic |
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Abstract: | Geometrical changes induced by cation substitutions {Si4+/Al3+}Mg2+/Al3+], {2Si4+/2Al3+} 2Mg2+/2Al3+], {Si4+/Fe3+} Mg2+/Al3+] or Mg2+/Fe3+], where {} and ] indicate tetrahedral and octahedral sheet in lizardite 1T, are studied by ab-initio quantum chemistry calculations. The majority of the models are based on the chemical compositions
reported for various lizardite polytypes with the amount of Al in the tetrahedral sheets reported to vary from 3.5% to 8%
in the 1T and 2H
1, up to ~30% in the 2H
2 polytype. Si4+ by Fe3+ substitution in the tetrahedral sheet with an Al3+ (Fe3+) in the role of a charge compensating cation in the octahedral sheet is also examined. The cation substitutions result in
the geometrical changes in the tetrahedral sheets, while the octahedral sheets remain almost untouched. Substituted tetrahedra
are tilted and their basal oxygens pushed down from the plane of basal oxygens. Ditrigonal deformation of tetrahedral sheets
depends on the substituting cation and the degree of substitution. |
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Keywords: | Ab-initio Pseudopotential Plane waves Lizardite Substitutions |
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