Evidence of a phase transition of RbHCO3 from high-resolution solid-state 13C and 87Rb NMR by comparison with KHCO3
✍ Scribed by Christophe Odin
- Publisher
- John Wiley and Sons
- Year
- 2004
- Tongue
- English
- Weight
- 462 KB
- Volume
- 42
- Category
- Article
- ISSN
- 0749-1581
- DOI
- 10.1002/mrc.1357
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✦ Synopsis
Abstract
A variable‐temperature high‐resolution ^13^C and ^87^Rb solid‐state NMR study of powder rubidium hydrogencarbonate, RbHCO~3~, is presented for the first time. At ambient temperature, RbHCO~3~ is formed by centrosymmetric dimers linked by hydrogen bonds, but almost no information is available on this compound concerning proton disorder and the low‐temperature phase. However, potassium hydrogencarbonate, KHCO~3~, which has an isomorphic structure for the high temperature phase, was well studied: it undergoes a non‐ferroic, non‐ferroelectric phase transition at T~c~ = 318 K between two monoclinic structures. The protons are disordered in an asymmetric double‐well potential in the low‐temperature phase, and the double‐well potential becomes symmetric in the high‐temperature phase. By comparison with recent solid‐state NMR experimental results on KHCO~3~, we show that RbHCO~3~ undergoes a phase transition at T~c~ ≈ 245 K, and give evidence that the proton dynamic disorder in both compounds is very similar. Copyright © 2004 John Wiley & Sons, Ltd.