On the Occupancy of Carbon Dioxide Clathrate Hydrates: Grandcanonical Monte Carlo Simulations

Abstract

Grandcanonical Monte Carlo simulations are performed in order to examine the cage occupancies of carbon dioxide clathrate hydrate in both the larger and the smaller cages, the latter of which has been controversial issue and is related significantly with its phase behavior. It is found that occupancy of CO 2 in the smaller cage of clathrate structure I is negligible at a pressure of CO 2 below 1 MPa while that in the larger cage increases gradually with increasing the pressure of CO 2 in equilibrium with the clathrate hydrate. It is suggested by the present simulations that CO 2 clathrate hydrate exhibits a different character in occupancy from ethane, which is a little larger than CO 2 and cannot enter into the smaller cage.

Adsorption of Formamide at the Surface of Amorphous and Crystalline Ices under Interstellar and Tropospheric Conditions. A Grand Canonical Monte Carlo Simulation Study

“…Indeed, the GCMC method has successfully been used to simulate the adsorption of various small molecules at the surface of, among others, clay minerals (e.g., kaolinite), 48,49 zeolites, 50-56 various metal oxides, 57-60 crystalline 26,61-69 as well as amorphous ice, 70 various carbonaceous materials, [71][72][73][74][75][76][77] self-assembled aerosol monolayers, 78,79 and covalent organic frameworks, [80][81][82] as well as inside protein crystals 83 and clathrate cages. [84][85][86][87][88][89][90][91] In this paper, we investigate in detail the adsorption of formamide both at the surface of Ih ice (at 200 K) and at the surface of LDA ice (at 200 K, 100 K, and 50 K). Although the adsorption on LDA at 200 K has relevance neither in atmospheric chemistry nor in astrochemistry, we included this system in the present investigation for reference purposes.…”

A comprehensive review on molecular dynamics simulation studies of phenomena and characteristics associated with clathrate hydrates

“…Studying 100% to 75% fractional occupancy at a certain condition indicated that the lower the cage occupancy, the higher the diffusion coefficient [327]. According to MD analysis, the rate of fractional occupancy in the small cavities of sI hydrate at the pressure ranges below 1 MPa was found to be insignificant but gradually increases with elevating the pressure [328]. Recently, the intracage behaviour of guest molecules in doubly occupied large cavities of sII hydrates at 100 K was probed by AIMD simulations in which the qualitative consistency of tetrahedral sites with the neutron scattering classical diffusion findings was confirmed [329].…”