DIFFUSE NEUTRON-SCATTERING STUDY OF DEUTERATED ICE IH

A series of measurements of the diffuse scattering from D2O ice Ih hav e been performed on SXD at ISIS using the neutron time-of-flight Laue diffraction technique. A large region of reciprocal space was covered in the three main planes of the hexagonal lattice, hk0, hhl and h0l, a t 20 K, and also in the hk0 plane at 10, 110, 160 and 250 K. The data show highly structured strong diffuse streaks, which are predominantly a result of static disorder in the lattice. Not all this scattering c an be explained in terms of the Bernal-Fowler rules, as a comparison w ith simulation shows. The changes in scattering in the hk0 plane with increasing temperature appear to be consistent with an increase in ato mic thermal vibrations, suggesting that the structural feature causing the scattering over and above the Bernal-Fowler prediction is present up to 250 K.