9. Advances in Molecular Simulation Studies of Clay Minerals

The unique structure and behavior of swelling clay minerals, as observed in the laboratory and in the environment, present a challenge in understanding of the molecular details associated with these minerals. The chapter introduces the essence of classical methods involving empirically derived potential energy expressions that allow simulation of periodic cells representing bulk and interfacial clay mineral systems. The classical models provide the simulation and analysis of many thousands to more than a million atoms for evaluating structures, adsorption, diffusion, intercalation, physical, and other properties. Quantum chemical calculations, including molecular orbital methods and density functional theory, optimize the configuration of electrons about atoms from first principles, but require significant computational cost to examine many of the important topics in clay mineralogy. Molecular simulation methods such as energy minimization, molecular dynamics, Monte Carlo techniques, vibrational analysis, thermodynamics calculations, transition state analysis, and a variety of related computational methods are utilized to improve our understanding of clay minerals, and to better interpret traditional characterization and spectroscopic methods. An example showing the use of molecular simulation for clay minerals is presented for the process of montmorillonite’s swelling as a function of interlayer water.