Kazuki Komatsu

Pressure Response on Hydrogen Bonds in Potassium Hydrogen Carbonate and Sodium Hydrogen Carbonate

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.