Simulating Liquid Water near Mineral Surfaces: Current Methods and Limitations

Abstract

It is important to propose molecular and theoretical models to describe the forces, energy, structure and dynamics of water near mineral surfaces. Our understanding of experimental results concerning hydration forces, the hydrophobic effect, swelling, reaction kinetics and adsorption mechanisms in aqueous colloidal systems is rapidly advancing as a result of recent Monte Carlo (MC) and molecular dynamics (MD) models for water properties near model surfaces. This paper reviews the basic MC and MD simulation techniques, compares and contrasts the merits and limitations of various models for water-water interactions and surfacewater interactions, and proposes an interaction potential model which would be useful in simulating water near hydrophilic surfaces. In addition, results from selected MC and MD simulations of water near hydrophobic surfaces are discussed in relation to experimental results, to theories of the double layer, and to structural forces in interfacial systems. Recent evidence (1) suggests that reactions at the mineral/liquid interface were involved in the beginnings of life on Earth.Not surprisingly, the nature and properties of mineral/water interfaces are of interest to physicists, chemists, physical chemists, applied mathematicians, colloid scientists, geochemists, soil scientists and civil engineers. Of particular interest is an increased understanding of the role of water in colloidal swelling, solute hydration, reaction kinetics, adsorption mechanisms, and ion exchange.The theoretical study (2,3) of this interface is made inherently difficult by virtue of the complex, many-body nature of the interaction potentials and forces involving surfaces, counterions, and water. Hence, many models of the interfacial region explicitly specify the forces between colloidal particles or between solutes, but few account for the many-body interaction forces of the solvent.

Atomic theories of phyllosilicates: Quantum chemistry, statistical mechanics, electrostatic theory, and crystal chemistry

“…The MD simulation by Dernontis et al[1983] is far more primitive than the other simulations and will not be discussed here. A review of statistical-mechanical simulations is timely, since many significant developments have appeared after this subject was reviewed byMulla [ 1986].Thestudies by Mulla et al [ 1984a, b] and He et al [ 1987] came from the same research group and describe similar findings. The microcanonical ensemble used in these simulations treated the phyllosilicate-water as an isolated system at constant energy, mass, and volume.…”