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C. Larvor, B. Stöger:
"The phase transition of rubidium hydrogen carbonate, RbHCO₃";
Acta Crystallographica Section E: Crystallographic Communications, E73 (2017), S. 975 - 979.

Rubidium hydrogen carbonate, RbHCO₃, features an order/disorder phase transition at T_C = 245 K from the high-temperature (HT) disordered C2/m modification to the low-temperature (LT) C-1 modification. The crystal structures are characterized by [HCO₃]₂²⁺ pairs of hydrogen carbonate groups connected by strong hydrogen bonding. The [HCO₃]₂²⁺ pairs are connected by Rb⁺ cations into a three-dimensional network. In HT-RbHCO₃, the hydrogen atom is disordered. In LT-RbHCO₃, ordering of the hydrogen atom leads to a translationengleiche symmetry reduction of index 2. The lost reflections and rotations are retained as twin operations.

crystal structure; order/disorder transition; hydrogen carbonate

http://dx.doi.org/10.1107/S2056989017008271

http://publik.tuwien.ac.at/files/publik_260000.pdf