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Updated: Aug 2, 2026

High Pressure Single Crystal Diffraction at PX^2
Published on: January 16, 2017
Transverse and longitudinal crystal modes associated with OH stretching vibrations in single crystals of kaolinite
1Macaulay Land Use Research Institute, Craigiebuckler, Aberdeen, UK. c.farmer@mluri.sari.ac.uk
Abstract:
Raman spectra of randomly-oriented kaolinite, dickite and nacrite show, for coarsely crystalline material, an extra band in the OH stretching region which is absent from the IR spectra of clay-size samples. Oriented single-crystal Raman spectra of these minerals provide confirmation for the assignment of the extra bands to transverse optical modes involving in-phase coupled vibrations of the layer-surface hydroxyl groups. The corresponding IR bands have transition moments nearly perpendicular to the layer surface, and appear at the higher frequencies of the longitudinal optical modes of macroscopic crystals.
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