Ab initio molecular dynamics calculations of ion hydration free energies

AUTOR(ES)

Leung, Kevin

FONTE

American Institute of Physics

RESUMO

We apply ab initio molecular dynamics (AIMD) methods in conjunction with the thermodynamic integration or “λ-path” technique to compute the intrinsic hydration free energies of Li+, Cl−, and Ag+ ions. Using the Perdew–Burke–Ernzerhof functional, adapting methods developed for classical force field applications, and with consistent assumptions about surface potential (ϕ) contributions, we obtain absolute AIMD hydration free energies (ΔGhyd) within a few kcal∕mol, or better than 4%, of Tissandier et al.’s [J. Phys. Chem. A 102, 7787 (1998)] experimental values augmented with the SPC∕E water model ϕ predictions. The sums of Li+∕Cl− and Ag+∕Cl− AIMD ΔGhyd, which are not affected by surface potentials, are within 2.6% and 1.2 % of experimental values, respectively. We also report the free energy changes associated with the transition metal ion redox reaction Ag++Ni+→Ag+Ni2+ in water. The predictions for this reaction suggest that existing estimates of ΔGhyd for unstable radiolysis intermediates such as Ni+ may need to be extensively revised.

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