Lattice dynamical simulation of methane hydrate

INS (Inelastic Neutron Scattering) spectrum of methane hydrate was measured on MARI (a direct-geometry chopper spectrometer) at Rutherford Appleton Laboratory, UK. Compared with ice Ih, it is found that the whole spectrum of methane hydrate moves toward high-energy by about 1.5 meV. Using lattice dynamical (LD) technique, computer simulations of methane hydrate were carried out. In the simulations, four potential models (BF, TIP3P, TIP4P, MCY) were employed to calculate the phonon density of states (PDOS). Comparing the calculated PDOS spectrum with the experimental spectrum, it is found that BF, TIP4P, and TIP3P potential lattices give out well-separated translational and librational bands while MCY potential lattice is unstable to do so and this model is not suitable to describe hydrate system.