Gas Hydrate Single-Crystal Structure Analyses

The first single-crystal diffraction studies on methane, propane, methane/propane, and adamantane gas hydrates SI, SII, and SH have been performed. To circumvent the problem of very slow
crystal growth, a novel technique of in situ cocrystallization of gases and liquids resulting in oligocrystalline
material in a capillary has been developed. With special data treatment, termed oligo diffractometry, structural
data of the gas hydrates of methane, acetylene, propane, a propane/ethanol/methane-mixture and an
adamantane/methane-mixture were obtained. Cell parameters are in accord with reported values. Host
network and guest are subject to extensive disorder, reducing the reliability of structural information. It was
found that most cages are fully occupied by a guest molecule with the exception of the dodecahedral cage
in the acetylene hydrate which is only filled to 60%. For adamantane in the icosahedral cage a disordered
model is proposed.