Neutron diffraction study of carbon dioxide clathrate hydrate

Neutron powder diffraction data of deuterated CO2 clathrate hydrate were me asured at 7, 48, 98, 148, and 213 K. Rietveld analysis revealed that the th ermal parameters of the atoms of the CO2 molecule in the tetrakaidecahedral cage are very large and almost constant in the whole temperature range. Th is result indicates that the CO2 molecule in the tetrakaidecahedral cage ro tates rapidly even at low temperatures. The interaction between the CO2 mol ecule and the deuterium atoms is so strong to provide the site dependence o f the thermal parameters of the deuterium atoms. (C) 1999 Elsevier Science Ltd. All rights reserved.