Molecular Modelling of Pore Fluids in Clays

Abstract

Recent advances in statistical mechanical molecular modelling of clay-fluid interactions will be discussed, with emphasis on empirical potential based Monte Carlo and molecular dynamics simulations. These methods will be illustrated by reference to the structure and dynamics of ions and solvent at hydrated clay surfaces. The aim of this research is to provide molecular scale insight into fluid dependent processes, for example; clay swelling, solute transport through clays, and clay compaction during burial. Models for the interparticle interactions will be reviewed, with particular reference to the various strategies used to represent clay-fluid systems. The general principles of Monte Carlo and molecular dynamics computer simulation will then be described. A number of specific issues arise when these techniques are applied to the properties of confined fluids: long-range interactions, system size limitations, boundary conditions, choice of thermodynamic ensemble, and statistical sampling. Throughout, we will compare and contrast recent computer simulations of clay-fluid systems with experimental data, and draw general lessons from these examples.