Where are Protons and Deuterons in KH _p D_{1 – p} CO₃? A Neutron Diffraction Study

Abstract

The crystals of potassium hydrogen carbonate (KHCO 3 ) and the KDCO 3 analogue are isomorphous. They are composed of hydrogen or deuterium bonded centrosymmetric dimers (HCOThe space group symmetry of KH p D 1−p CO 3 (p ≈ 0.75) determined with neutron diffraction is identical to those of KHCO 3 and KDCO 3 . 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. WidmungIt is a great pleasure to dedicate this paper to Professor Hans-Heinrich Limbach on the occasion of his sixty fifth birthday, and to wish him many more happy and productive years of activity in chemistry.2