Affiliations: Laboratory for Earthquake Chemistry, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan | Department of Earth and Space Science, Graduate School of Science, Osaka University, Osaka 560-0043, Japan | Institute of Mineralogy, Petrology, and Economic Geology, Graduate School of Science, Tohoku University, Miyagi 980-8578, Japan | Department of Physics and Astronomy, The University of Edinburgh, Edinburgh EH93JZ, UK | Departments of Geosciences and Chemistry, SUNY at Stony Brook, Stony Brook, NY 11794-2100, USA
Note: [] Present address: Department of Earth and Planetary Materials Science, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan.
Abstract: Pressure responses of hydrogen bonding interactions were compared between potassium hydrogen carbonate (KHCO3) and sodium hydrogen carbonate (NaHCO3). KHCO3 undergoes a pressure-induced structural change at 2.8 GPa and room temperature whereas no phase transition has been found so far for NaHCO3 up to 11 GPa. KHCO3 exhibits a substantial decrease in the O—H···O angle with increasing pressure. This change could be a trigger for the phase transition at 2.8 GPa. By contrast, no significant change in O—H···O angle was observed for NaHCO3 up to 7 GPa. Based on the observations using neutron diffraction, X-ray diffraction and vibrational spectroscopy at high pressure, a possible mechanism for the phase transition of KHCO3 is suggested. In addition, the phase boundary of KHCO3 caused by the pressure-induced transition was determined using in situ Raman spectroscopy at high pressure.
