Fig. 3: The rotor-lattice coupling in MH-III.
a, b The vibrational density of states (VDOS) of (a) host H2O lattices and (b) guest CH4 molecules at different pressures. The dashed lines denote the VDOS profiles of the center-of-mass (COM) of the molecules showing only the translational contribution; the resulting differences between the solid and dashed lines expose the rotational/librational contribution. There are additional CH4 bending, rocking, and stretching modes with extremely high frequencies (> 40 THz). Their contributions to the total TC are minor (see Supplementary Note 3 and Supplementary Fig. 9). c The rotational density of states (RDOS) of CH4 molecules. d The first-order Legendre reorientational correlation functions (RCFs) C1(t) of CH4 molecules under the NVT (constant volume and temperature) ensemble at 3 GPa (blue) and 60 GPa (red). The black lines denote the average of all CH4 molecules in the simulation box. The gray line shows the oscillations of the individual RCF curve at 3 GPa. e The average first-order (solid lines) and second-order (dashed lines) RCFs Cn (t) of CH4 molecules at different pressures. f The average first-order CH4-RCFs at 3 GPa (blue) and 60 GPa (red) with the vibrating H2O lattice (solid lines) and the fixed one (dash-dotted lines). The curves are plotted in the logarithmic scale to clarify the non-exponential behavior. Source data are provided as a Source Data file.
