01985nas a2200169   4500008004100000022001400041245011400055210006900169260007100238300001600309490000800325520129200333100002601625700001901651700001501670856013001685       2013                        eng d  a1932-744700aHeat transfer calculations for decomposition of structure i methane hydrates by molecular dynamics simulation0 aHeat transfer calculations for decomposition of structure i meth  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcJUN  a12172-121820 v1173 a<p>Microcanonical ensemble molecular dynamics simulations of structure I methane hydrate is presented in this work to study the endothermic decomposition process. The mechanism of decomposition of methane hydrate as a function of time was explained at the molecular level. The initial temperature and pressure of the simulation were chosen so as to depict the natural gas hydrate in conditions of oceanic sediments. A more realistic strategy was developed to perform the microcanonical ensemble simulation of solid liquid interface of hydrate and amorphous water. Two water models, SPC/E and TIP4P, were used for the simulations, and the results of the simulations were compared. Heat transfer calculations were performed on the adiabatic system, and an attempt has been made to fit the MD simulation results to the heat balance equations derived from the heat transfer calculations. Estimates of the properties at the macroscopic scale, like the equilibrium temperature of methane hydrate and rate of supply of hot water for sustained release of methane from solid hydrate phase, were determined. The equilibrium temperature obtained by the above method was found to be in agreement with the experimentally observed value. Both the SPC/E and TIP4P water models gave similar results.</p>1 aBaghel, Vikesh, Singh1 aKumar, Rajnish1 aRoy, Sudip  uhttps://library.ncl.res.in/content/heat-transfer-calculations-decomposition-structure-i-methane-hydrates-molecular-dynamics-002612nas a2200181   4500008004100000022001400041245014000055210006900195260011000264300001400374490000700388520182900395100001802224700002602242700001502268700001902283856012802302       2015                        eng d  a1463-907600aMolecular dynamics study of model SI clathrate hydrates: the effect of guest size and guest-water interaction on decomposition kinetics0 aMolecular dynamics study of model SI clathrate hydrates the effe  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcFEB  a9509-95180 v173 a<p>One of the options suggested for methane recovery from natural gas hydrates is molecular replacement of methane by suitable guests like CO2 and N-2. This approach has been found to be feasible through many experimental and molecular dynamics simulation studies. However, the long term stability of the resultant hydrate needs to be evaluated; the decomposition rate of these hydrates is expected to depend on the interaction between these guest and water molecules. In this work, molecular dynamics simulation has been performed to illustrate the effect of guest molecules with different sizes and interaction strengths with water on structure I (SI) hydrate decomposition and hence the stability. The van der Waals interaction between water of hydrate cages and guest molecules is defined by Lennard Jones potential parameters. A wide range of parameter spaces has been scanned by changing the guest molecules in the SI hydrate, which acts as a model gas for occupying the small and large cages of the SI hydrate. All atomistic simulation results show that the stability of the hydrate is sensitive to the size and interaction of the guest molecules with hydrate water. The increase in the interaction of guest molecules with water stabilizes the hydrate, which in turn shows a slower rate of hydrate decomposition. Similarly guest molecules with a reasonably small (similar to Helium) or large size increase the decomposition rate. The results were also analyzed by calculating the structural order parameter to understand the dynamics of crystal structure and correlated with the release rate of guest molecules from the solid hydrate phase. The results have been explained based on the calculation of potential energies felt by guest molecules in amorphous water, hydrate bulk and hydrate-water interface regions.</p>1 aDas, Subhadip1 aBaghel, Vikesh, Singh1 aRoy, Sudip1 aKumar, Rajnish  uhttps://library.ncl.res.in/content/molecular-dynamics-study-model-si-clathrate-hydrates-effect-guest-size-and-guest-water-0