A Priori Approach to Calculation of Energies of Solvation
  We propose a systematic, {\em a priori} approach to the problem of the calculation of solvation energies using continuum dielectric models coupled to quantum mechanical description of reacting molecules. Our method does not rely on empirically scaled van der Waals radii to create a dielectric cavity, but rather uses the electron density of the reactants as the physical variable describing the cavity. In addition, the precise choice of cavity is made by ensuring that the dielectric reproduces the correct linear response of the solvent to electrostatic perturbations. As a model application which is interesting in its own right, we study the hydrolysis of methylene chloride, a representative model waste compound in supercritical oxidation experiments, and which has shown surprising solvation effects close to the critical point of pure water (T=394$^o$ C, P=221 bar). Using our {\em a priori} methodology, we find results in good agreement with available experimental reaction barriers. We then study, in a controlled manner, the relative importance of various further approximations that are routinely performed in the literature such as the use of spherical cavities, the replacement of the reactant by a dipole, or the neglect of self consistency in solving the electrostatic problem. 
Sohrab Ismail-Beigi, T. A. Arias, Phillip Marrone, Matthew Reagan,   Jefferson W. Tester