Transformation of hydrogen bond network during the CO2 clathrate hydrate dissociation

TL;DR

This study investigates the structural changes in hydrogen bonding during CO2 hydrate melting using molecular dynamics, revealing rapid reorganization of water molecules and a slight decrease in hydrogen bonds.

Contribution

It provides detailed molecular-level insights into hydrogen bond network transformation during CO2 hydrate dissociation, highlighting rapid reorganization and energy stability.

Findings

Approximately 10-15% decrease in H-bond number after melting

Instant reorganization of short-range order within less than 1 nanosecond

Minor changes in H-bond interaction energy during phase transition

Abstract

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.