In recent history there has been an increase in interest in the theoretical modeling of chemical systems; both as a method of better understanding how these systems work, and as a more economical way of exploring new areas in chemistry. The research and development of new and improved computer systems aid greatly in the extent and detail to which we can model these systems. Due to this fact, computational chemistry may be a large part of the future of chemistry.

Through the use of a Silicon Graphics workstation, I will be attempting to model a clay/ion system and monitor how this system reacts to the increase and decrease of humidity in the environment. This will be the first computer simulation study of a calcium-clay system at varying water contents. These clays consist of extremely thin sheets composed of three bonded layers. The middle layer consists of aluminum ions which are octahedrally bonded to adjacent oxygen atoms, and this is surrounded on both sides by a tetrahedrally bonded silicon dioxide layers. These sheets stack on top of each other to form a clay deposit. However, between these layers ions exist to balance the negative charge at the clay surface. These ions settle over charged sites in the clay, thus strengthening it. In the environment, water molecules also absorb into the gaps between the clay layers, increasing the distance between them. At certain water contents the clay is much more stable then at others, and if the water content is too high the clay particles may disperse, a phenomenon known as flocculation. The purpose of this research will be to model these systems and find at what water contents these clays are most stable. This will be done by finding the energy minimum for each level.

Also as a byproduct of this research we hope to determine how many waters are contained in the solvation shells of the calcium ions in our system. This is important because to date this is not known. In this system, the water molecules also serve to stabilize the structure. This stabilization occurs through hydrogen bonding of the water molecules to the clay surface. This additional bonding helps to hold the ions in place.

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