Transition from cage clathrate to filled ice: the structure of methane hydrate III

Phys Rev Lett. 2001 Nov 19;87(21):215501. doi: 10.1103/PhysRevLett.87.215501. Epub 2001 Oct 31.


The structure of a new methane hydrate has been solved at 3 GPa from neutron and x-ray powder diffraction data. It is a dihydrate in which a 3D H-bonded network of water molecules forms channels surrounding the methane molecules. The network is closely related to that of ice-Ih and the methane-water system appears to be the first in which a cage clathrate hydrate is transformed into an ice-related hydrate (a "filled ice").