The phase transition of rubidium hydrogen carbonate, RbHCO3

Abstract

Rubidium hydrogen carbonate, RbHCO3, features an order/disorder phase transition atTC= 245 K from the high-temperature (HT) disorderedC2/mmodification 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 atranslationengleichesymmetry reduction of index 2. The lost reflections and rotations are retained as twin operations.