Abstract
The fundamental properties of gas hydrates are reviewed; classification and type, structure and composition, formation and stability, and occupancy of guest molecules. Recent Raman studies on the properties of cage-occupancy are discussed by considering the C-H vibrations of their guest molecules for methane, methane-ethane mixed (structural phase transition), ethane, and cyclopropane (pressure-induced small cage occupancy) hydrates. Finally, I give an overview of very recent x-ray (neutron) diffraction and Raman scattering studies of phase transitions in the methane hydrate at high pressures, and discuss the inconsistent results by investigating the experimental details.
