Fig. 1. Phase equilibrium condition curves of clathrate hydrates with different guest molecules^［3］

Fig. 2. Schematic diagram of common hydrate crystal structure^［14］

Fig. 3. Schematic diagram of the relationship between methane hydrate formation process and methane gas consumption （constant pressure， constant temperature） over time^［41］

Fig. 4. Schematic diagram of unstable cluster nucleation hypothesis^［44］

Fig. 5. Molecular dynamics simulation results of hydrate cluster structure evolving with time^［23］

Fig. 6. Nucleation mechanism of blob hypothesis based on molecular dynamics simulation^［26］

Fig. 7. The growth process of hydrate on the surface^［50］

Fig. 8. Schematic diagram of memory effect： the curve of continuous rise and fall of methane hydrate^［52］

Fig. 9. Infrared and Raman spectra of methane hydrate

Fig. 10. Neutron diffraction spectrum and X-ray diffraction spectrum of methane hydrate

Fig. 11. Simulation results of the density distribution of methane and water molecules at the methane-water interface^［64］

Fig. 12. Schematic diagram of non-collinear sum-frequency vibration spectrum measurement system and femtosecond amplifier system

Fig. 13. Raman spectrum of water （D₂O） at a temperature of 4.3 ℃， 0.1 MPa （1 atm） and 8.0 MPa methane gas pressure

Fig. 14. Sum frequency vibrational spectrum of methane hydrate at the interface

Fig. 15. Changes of Dangling-OD during the formation of methane hydrate

Fig. 16. Sum-frequency vibrational spectroscopy results before and after forming a thin layer of hydrate and remelting

Fig. 17. Schematic diagram of the formation process of methane hydrate at the methane-water gas-liquid interface