Where are Protons and Deuterons in KH p D1 – p CO3? A Neutron Diffraction Study

Abstract

Abstract The crystals of potassium hydrogen carbonate (KHCO3) and the KDCO3 analogue are isomorphous. They are composed of hydrogen or deuterium bonded centrosymmetric dimers (HCO3 –)2 or (DCO3 –)2. The space group symmetry of KH p D1 – p CO3 (p ≈ 0.75) determined with neutron diffraction is identical to those of KHCO3 and KDCO3. This is at variance with a random distribution of H and D nuclei. These crystals are macroscopic quantum systems in which protons or/and deuterons merge into macroscopic states.