Structural transformation of methane hydrate from cage clathrate to filled ice

Ikeda, Takashi; Terakura, Kiyoyuki*

The structural, dynamical, and electronic properties of methane hydrate under pressure and at room temperature are investigated using the constant pressure molecular dynamics method. Cage structures in cubic structure I are destroyed at 4.5GPa. After the breakdown of cage structures water molecules form a channel surrounding a chain of methane molecules prominent in MH-III. In our MH-III there exists a single peak of C-D stretching mode showing blueshift in agreement with experiment. Our study supports the existence of [Phys. Rev. Lett. , 215501 (2001).]