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Normal Coordinate Analysis of Benitoite (BaTiSi3O9) and its Constituent Ring

Published online by Cambridge University Press:  01 January 1992

Charles C. Kim
Affiliation:
Naval Research Laboratory, Dynamics of Solids Branch, Washington, D.C. 20375-5320
M. I. Bell
Affiliation:
Naval Research Laboratory, Dynamics of Solids Branch, Washington, D.C. 20375-5320
D. A. McKeown
Affiliation:
Chemistry Dept., Howard University, Washington, D.C. 20059
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Abstract

The normal modes of vibration and their frequencies are calculated for benitoite, a mineral whose crystal structure (space group D23h) consists of three-membered silicate rings (Si3O9) linked by Ba+2 and Ti+4 ions. The calculation unambiguously assigns the normal modes to the lines in the Raman and infrared spectra and determines the atomic interactions. On the assumption that mode mixings and splittings due to inter-ring interactions are small, the normal frequencies of the isolated ring of C3h, symmetry are determined. The identification of normal modes characteristic of three-membered silicate rings may prove to be a valuable guide in the interpretation of the infrared and Raman spectra of amorphous silicates, potentially leading to new information on the ring statistics of these materials.

Type
Research Article
Copyright
Copyright © Materials Research Society 1993

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References

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