Elasticity and Stability of Clathrate Hydrate: Role of Guest Molecule Motions.

ABSTRACT: Molecular dynamic simulations were performed to determine the elastic constants of carbon dioxide (CO₂) and methane (CH₄) hydrates at one hundred pressure-temperature data points, respectively. The conditions represent marine sediments and permafrost zones where gas hydrates occur. The shear modulus and Young's modulus of the CO₂ hydrate increase anomalously with increasing temperature, whereas those of the CH₄ hydrate decrease regularly with increase in temperature. We ascribe this anomaly to the kinetic behavior of the linear CO₂ molecule, especially those in the small cages. The cavity space of the cage limits free rotational motion of the CO₂ molecule at low temperature. With increase in temperature, the CO₂ molecule can rotate easily, and enhance the stability and rigidity of the CO₂ hydrate. Our work provides a key database for the elastic properties of gas hydrates, and molecular insights into stability changes of CO₂ hydrate from high temperature of ~5?°C to low decomposition temperature of ~-150?°C.

SUBMITTER: Jia J 

PROVIDER: S-EPMC5431056 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature