Monte Carlo Simulation of Interlayer Molecular Structure in Swelling Clay Minerals. 1. Methodology

N. T. Skipper1, Fang-Ru Chou Chang2 and Garrison Sposito2
1 Department of Physics and Astronomy, University College, Gower Street, London WC1E 6BT, UK
2 Department of Environmental Science, Policy, and Management University of California, Berkeley, California 94720-3110

Abstract: Monte Carlo (MC) simulations of molecular structure in the interlayers of 2:1 Na-saturated clay minerals were performed to address several important simulation methodological issues. Investigation was focused on monolayer hydrates of the clay minerals because these systems provide a severe test of the quality and sensitivity of MC interlayer simulations. Comparisons were made between two leading models of the water-water interaction in condensed phases, and the sensitivity of the simulations to the size or shape of the periodically-repeated simulation cell was determined. The results indicated that model potential functions permitting significant deviations from the molecular environment in bulk liquid water are superior to those calibrated to mimic the bulk water structure closely. Increasing the simulation cell size or altering its shape from a rectangular 21.12 Å x 18.28 Å 6.54 Å cell (about eight clay mineral unit cells) had no significant effect on the calculated interlayer properties.

Key Words: Clay-water systems • Monte Carlo simulation • Swelling clays

Clays and Clay Minerals; June 1995 v. 43; no. 3; p. 285-293; DOI: 10.1346/CCMN.1995.0430303
© 1995, The Clay Minerals Society
Clay Minerals Society (www.clays.org)