Gas Hydrates and Permafrost 329 Intermolecular potentials in gas hydrates

• Main Authors: J. S. Tse, D. W. Davidson
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Langmuir; permafrost
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.551.1285; http://pubs.aina.ucalgary.ca/cpc/CPC4-329.pdf

From a new set of Lennard-Jones (L-J) potential parameters for water derived from relatively accu-rate theoretical calculations, the dissociation pressure and cage occupancy ratio of some structure I gas hydrates are calculated within the localized site- solid solution model. The cell partition functions are evaluated in both the Devonshire spherical-cell approximation and by rigorous Monte Carlo inte-gration. The two methods gave satisfactory, and closely similar, results. The low occupancies of the small cages of the xenon and CF, hydrates observed experimentally are reproduced and may be ex-plained primarily as a size effect of the encaged molecules. A procedure based on the more rigorous theory of intermolecular forces is used to construct more-realistic exp-6-8-10 potential functions for unlike pair interactions. Preliminary calculations of the Langmuir constants for some gas hydrates appear to demonstrate the superiority of the exp-6-8-10 potential over the L-J potential. The require-ments for further improvement are discussed. A partir d'un nouvel ensemble de parametres potentiels de Lennard-Jones (L-J) relatifs a I'eau, deri-ves de calculs theoriques relativement precis, on a calcule la pression de dissociation et le rapport d'in-sertion de certains hydrates gazeux de structure I a I'interieur du modele qui reprksente un site precis et une solution solide. On a evalui les fonctions de partition des cellules a la fois selon I'approximation