The electron density distribution in ice Ih determined by single‐crystal x‐ray diffractometry

Precise structure analysis of ice Ih was carried out by single-crystal x-ray diffractometry. The reliability factor R was as small as 0.007 for the refined structure based on the half-hydrogen model. Both of the O–H distances at 243 K, those oblique and parallel to the c axis, were determined to be 0.85(2) and 0.82(3) Å, respectively, which are significantly shorter than those determined by the neutron diffraction method. These discrepancies were attributed to the difference between the electron and protonic density distribution along the O–H---O bond. Fourier synthesis and difference synthesis were computed for clarifying the electron density distribution relating to the hydrogen bonding.