  Microwave heating of methane hydrate is investigated with electrostatic
molecular dynamics simulations by the SPC/E water model. The structure I of
methane hydrate is constructed. When the methane hydrate with a density of 0.91
$\rm{g/cm}^3$ and temperature of 273 K is exposed to microwave electric fields,
it suddenly collapses in liquid after a certain period of irradiation. However,
a hydrate with a five percent higher density of 0.95 $\rm{g/cm}^3$ and the same
initial temperature shows no collapse as a crystal caused by the microwave. A
hydrate with CO$_{2}$ guest molecules has increased kinetic energy but rapidly
collapses due to the Lennard-Jones potentials. The methane hydrate with
variable density and temperature is presented and exhibits slow heating as a
crystal and an unchanging volume.
