MP2 hydration free energies of 20 different salts show excellent agreement with experiments

by Wang, Feng; Li, Jicun

Prediction of free energy information with only electronic structure calculation is challenging. With the adaptive force matching method developed in our group, the MP2 potential energy surfaces for hydrated alkali ions from Li+ to Cs+ and halide ions from F- to I- were mapped to simple pair-wise interaction potentials. For the 10 salts formed by F- and Cl- ions, the hydration free energies predicted by these MP2 based models agree with experiments within 2%. For the 10 salts formed by Br- and I- ions, the agreement is within 6%. No exptl. information was used during the development of the force field models. The resulting model also gives excellent agreement with exptl. diffusion constants Details of the hydration structures of the ions revealed by the MP2 based models will be discussed.