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

摘要

Pressure responses of hydrogen bonding interactions were compared between potassium hydrogen carbonate (KHCO_3) and sodium hydrogen carbonate (NaHCO_3). KHCO_3 undergoes a pressure-induced structural change at 2.8 GPa and room temperature whereas no phase transition has been found so far for NaHCO_3 up to 11 GPa. KHCO_3 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 NaHCO_3 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 KHCO_3 is suggested. In addition, the phase boundary of KHCO_3 caused by the pressure-induced transition was determined using in situ Raman spectroscopy at high pressure.