INCORPORATING SOLVATION EFFECTS INTO DENSITY-FUNCTIONAL ELECTRONIC-STRUCTURE CALCULATIONS

An improved approach to the calculation of molecular electronic structures, solvation energies, and pK(a) values in condensed phases is described. The electronic structure of the solute is described by density functional quantum mechanics, and electrostatic features of environmental effects are modeled through external charge distributions and continuum dielectrics. The reaction potential produced by atom-centered point-charge and dipole fits to the molecular charge distribution is computed via finite-difference solutions to the Poisson-Boltzmann equation. The coupling of the reaction potential into the molecular Hamiltonian is achieved through numerical integration, and the entire system is iterated to self-consistency. Sample calculations of solvation energies, solvated dipole moments, and absolute pK(a) values are provided for a variety of small organic molecules to illustrate applications of the method. This approach should be readily extensible to more complex systems such as proteins because it is straightforward to include counterion effects and multiple dielectric regions in the formulation.