Absolute hydration free energy scale for alkali and halide ions established from simulations with a polarizable force field.
A polarizable potential function for the hydration of alkali and halide ions is developed on the basis of the recent SWM4-DP water model [Lamoureux, G.; MacKerell, A. D., Jr.; Roux, B. J. Chem. Phys. 2003, 119, 5185]. Induced polarization is incorporated using classical Drude oscillators that are treated as auxiliary dynamical degrees of freedom. The ions are represented as polarizable Lennard-Jones centers, whose parameters are optimized to reproduce the binding energies of gas-phase monohydrates and the hydration free energies in the bulk liquid. Systematic exploration of the parameters shows that the monohydrate binding energies can be consistent with a unique hydration free energy scale if the computed hydration free energies incorporate the contribution from the air/water interfacial electrostatic potential (-540 mV for SWM4-DP). The final model, which can satisfyingly reproduce both gas and bulk-phase properties, corresponds to an absolute scale in which the intrinsic hydration free energy of the proton is -247 kcal/mol.
Lamoureux
Guillaume
G
Département de physique, Université de Montréal, C.P. 6128, succ. centre-ville, Montréal, Québec H3C 3J7, Canada.
Roux
Benoît
B
D000388:Air; D000838:Anions; D002412:Cations; D002627:Chemistry, Physical / Q000379:methods*; D003198:Computer Simulation; D007477:Ions; D008958:Models, Molecular; D015233:Models, Statistical; D055672:Static Electricity; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
D000838:Anions; D002412:Cations; D007477:Ions; D014867:Water