Ab initio calculations of relative stabilities of different structural arrangements in dioctahedral phyllosilicates

Daniel Tunega, Bernard A. Goodman, Georg Haberhauer, Thomas G. Reichenauer, Martin H. Gerzabek, Hans Lischka

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An ab initio theoretical approach has been used to calculate optimized geometries and the relative energies of various compositional arrangements in structures of dioctahedral smectites based on models consisting of two unit-cells. These calculations indicate that the energy differences between structures having vacancies in sites with cis- or trans-OH coordination are small and that their relative energies vary with the chemical nature of the substitutions. For example, a cis-OH coordination for the vacancy was the most stable when the interlayer charge originated from substitution of Al for Si in the tetrahedral sheet, whereas the trans-coordination was the more stable for most cases of substitution in the octahedral sheet, an exception being Fe(II) for Al where the cis-OH coordination was favored. It seems likely, therefore, that long-range structural disorder will be a common phenomenon in natural phyllosilicate specimens.

Original languageEnglish
Pages (from-to)220-232
Number of pages13
JournalClays and Clay Minerals
Issue number2
StatePublished - Apr 1 2007



  • Ab initio
  • Cis- and Trans-coordination
  • Dioctahedral
  • Phyllosilicates
  • Smectite

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