Generalized Born Solvation Model SM12.

We present a new self-consistent reaction-field implicit solvation model that employs the generalized Born approximation for the bulk electrostatic contribution to the free energy of solvation. The new solvation model (SM) is called SM12 (where ″12″ stands for 2012), and it is available with two sets of parameters, SM12CM5 and SM12ESP. The SM12CM5 parametrization is based on CM5 partial atomic charges, and the SM12ESP parametrization is based on charges derived from a quantum-mechanically calculated electrostatic potential (ESP) (in particular, we consider ChElPG and Merz-Kollman-Singh charges). The model was parametrized over 10 combinations of theoretical levels including the 6-31G(d) and MG3S basis sets and the B3LYP, mPW1PW, M06-L, M06, and M06-2X density functionals against 2979 reference experimental data. The reference data include 2503 solvation free energies and 144 transfer free energies of neutral solutes composed of H, C, N, O, F, Si, P, S, Cl, Br, and I in water and in 90 organic solvents as well as 332 solvation free energies of singly charged anions and cations in acetonitrile, dimethyl sulfoxide, methanol, and water. The advantages of the new solvation model over our previous generalized Born model (SM8) and all other previous generalized Born solvation models are (i) like the SMD model based on electron density distributions, it may be applied with a single set of parameters with arbitrary extended basis sets, whereas the SM8 model involves CM4 or CM4M charges that become unstable for extended basis sets, (ii) it is parametrized against a more diverse training sets than any previous solvation model, and (iii) it is defined for the entire periodic table.