Chang-Guo Zhan of the University of Kentucky is supported by an award from the Chemical Theory, Models and Computational Methods program, co-funded by the EPSCoR office of NSF, to develop a first-principles electronic structure method accounting for solvent effects. This is very commonly modeled as a dielectric continuum reaction field while the solute is treated quantum mechanically. Many practical reaction field implementations represent the solvent polarization through an apparent surface charge distribution on the boundary of the solute cavity. However, quantum mechanical calculations usually lead to a tail of the wave function penetrating outside the cavity, which produces an additional volume polarization to the reaction field. The PI and his research group are developing a generalized implementation of a unique reaction field method, known as the fully polarizable continuum model (FPCM), capable of accurately determining volume polarization, in addition to the commonly treated surface polarization, for a general, irregularly-shaped solute cavity. In particular, they are developing the analytic energy derivatives with respect to the nuclear coordinates of the solute for the FPCM method so that the FPCM implementation can be used for geometry optimization and vibrational frequency calculations of molecules in solution. In addition, they make use of the generalized implementation together with other available computational methods to study some representative chemical problems involving molecular structures, properties, and reaction mechanisms. Students will be involved in the project and trained in these computational methods.
This generalization of the FPCM method is of interest in a wide range of disciplines such as inorganic chemistry, organic chemistry, biochemistry, environmental chemistry, medicinal chemistry, and pharmaceutical sciences. In recent years the calculation of energies and geometries of isolated molecules has grown much more reliable. With the ability to determine molecular geometries of molecules in a crowded solution environment in much the same way, it is becoming possible to computationally investigate biomolecules in aqueous environments, chemical reactions in various solvents, charge redistribution for molecules in liquids, and so on.
