  The object of this study is the kinetic process of solid-liquid first-order
phase transition - melting of carbon dioxide CS-I hydrate with various cavity
occupation ratios. The work was done within a framework of study on the local
structure of water molecules. These include the time depending change of the
short-range order at temperatures close to the melting point and comparison
with hexagonal ice structure. Using 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 oxygen-oxygen radial distribution and
hydrogen-oxygen-oxygen mutual orientation angles between molecules detached at
no more than 3.2 angstroms allowed to find the H-bond coordination number of
all molecules and full number of H-bonds and showed the instant (less than 1
nanosecond) reorganization of short-range order of all molecules. The structure
analysis of every neighbor water molecules pairs showed the ~10-15 percents
decrease of H-bond number after the melting whereas all molecules form single
long-range hydrogen bond network. The analysis of hydrogen bond network showed
the minor changes in the H-bond interaction energy at solid-liquid phase
transition.
