Structure analysis of propane hydrates

Clathrate hydrates consist of water cages linked by hydrogen bonds, and various guest molecules. Propane hydrate contains propane as a guest molecule and has a structure II crystal structure. We synthesized propane deuterohydrate (C₃H₈ + D₂O) and deuterated propane hydrate (C₃D₈ + D₂O). Powder neutron diffraction data were collected from 10 K to 150 K on iMATERIA in J-PARC. The diffracted peaks of both C₃H₈ hydrate and C₃D₈ hydrate were almost in the same position; however, peak intensities between the two differed. We analyzed the crystal structure by the Rietveld method using Z-Rietveld program. Neutron diffraction patterns revealed that our samples were crystallized as structure II hydrate. In addition, there were some defects of deuterated propane in the cage of deuterated propane hydrate. (author)