Tetrahedral rigid-body motion in silicates

K. L. Bartelmehs, R. T. Downs, G. V. Gibbs, M. B. Boisen, J. B. Birch

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


The atomic displacement parameters (ADPs) obtained from published refinements of silicate crystals measured at or below room temperature are examined to determine if TO4 (T = Al,Si) tetrahedra display rigid-body thermal motion. In many cases, the correlation found among the ADPs is consistent with the TLS model of rigid-body motion. The libration angle for rigid tetrahedra is quadratically dependent on the difference between the isotropic equivalent displacement parameter of the T and O atoms, Beq(T) and Beq(O), respectively. The value of Beq(O) is on average twice that of Beq(T), with an observed maximum value of ~2.0 Å3. -from Authors

Original languageEnglish (US)
Pages (from-to)680-690
Number of pages11
JournalAmerican Mineralogist
Issue number7-8
StatePublished - 1995

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology


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