Extension of the MST model to the IEF formalism: HF and B3LYP parametrizations

An extension of the Miertus-Scrocco-Tomasi (MST) continuum method to the Integral Equation Formalism (IEF) is presented. In particular, we report here the parametrization of the MST(IEF) model to the solvation in water, octanol, chloroform and carbon tetrachloride. A detailed comparison is made between the results obtained from the MST(PCM) formalism corrected by using diverse charge normalization schemes and those obtained from the IEF formalism. The IEF method is found to provide results in close agreement with those obtained within the PCM framework by taking into account the anisotropy of the solute's charge distribution in the charge normalization of the apparent surface charge that simulates the solvent reaction field. Besides the standard HF/6-31G(d) level of theory considered in previous parametrizations of the MST(PCM) model, we also report here the results obtained for the B3LYP hybrid density functional method. These results indicate that there are small differences in the electrostatic component of the solvation free energy determined from HF and B3LYP levels of theory, which might be captured by suitable adjustment of the atomic surface tensions in the van der Waals component. Overall, the results support the strategy used in the development of the MST model and its suitability as a robust approach to the study of molecules in solution.