Transformation of hydrogen bond network during CO2 clathrate hydrate dissociation

K Gets and V Belosludov and R Zhdanov and Y Bozhko and R Belosludov and O Subbotin and N Marasanov and Y Kawazoe, APPLIED SURFACE SCIENCE, 499, 143644 (2020).

DOI: 10.1016/j.apsusc.2019.143644

The kinetic process of the solid-liquid first-order phase transition of carbon dioxide CS-I hydrates with various cavity occupation ratios has been investigated in order to understand the framework of the H-bond network and the local structure of each water molecule. This includes the time dependent change in short-range order at temperatures close to the melting point and comparison with the hexagonal ice structure. Using the molecular dynamics method, dependencies of the internal energy of the studied systems on the time of heating were found. Jumps in the internal energy of solids in the range at 275-300 K indicate a phase transition. The study of the oxygen-oxygen radial distribution and hydrogen-oxygen-oxygen mutual orientation angles between molecules detached at no > 3.2 angstrom led to the determination of the H-bond coordination number for all molecules and the total number of H-bonds and showed instantaneous (< 1 ns) reorganization of the short-range order of all molecules. Structural analysis of neighbor water molecule pairs showed similar to 10-15% decrease in the H-bond number after melting whereas all molecules form a single long-range H-bond network. Analysis of the H-bond network showed minor changes in the H-bond interaction energy at the solid-liquid phase transition.

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