Raman spectra of tetramethylammonium–trimethylammonium mixed ion vermiculite clay intercalation compounds
✍ Scribed by S. A. Solin; H. X. Jiang; H. Kim; T. J. Pinnavaia
- Publisher
- John Wiley and Sons
- Year
- 1990
- Tongue
- English
- Weight
- 500 KB
- Volume
- 21
- Category
- Article
- ISSN
- 0377-0486
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✦ Synopsis
Abstract
The composition dependence of the Raman spectra of the mixed ion vermiculites [(CH~3~)~4~N^+^]~1‐x~ [(CH~3~)~3~NH^+^]~x~‐V (V = vermiculite) have been studied in the range 0 ⩽ x ⩽ 1. The torsional mode frequencies exhibit a small shift (ca. 2 cm^−1^) to lower energy with increasing x and their composition dependence is distinct from that shown by the corresponding modes of Cs~1‐x~Rb~x~‐V. These differences are attributed to a variation of the guest‐host force constants and in particular to the interactions between the guest ions and the basal oxygens, which depend strongly on the size difference,Δ__D__, between the guest ion pairs. Using a van der Waals‐type force model and the nearest neighbor approximation, the torsional mode frequencies of the pure end‐member compounds of the two mixed ion systems discussed above have been successfully accounted for.