Combined ab initio quantum mechanical/molecular mechanical (QM/MM) molecular dynamics simulations have been performed to investigate the hydration shell properties of F− and Cl−. The chemically most relevant region, the hydration sphere of the anions, was treated by Born–Oppenheimer ab initio quantum mechanics using D95V+, 6-31+G and D95V++ basis sets for F−, Cl− and water, respectively, while the remaining part was described by classical pair potentials. The QM/MM simulations have predicted average coordination numbers of 4.6 ± 0.2 for F− and 5.6 ± 0.1 for Cl−, in contrast to the corresponding values of 5.8 ± 0.1 and 5.9 ± 0.1 resulting from classical pair potential simulations. Within the first hydration shell of F−, the QM/MM results indicate more flexibility of the hydration complex in which the F−⋯H–O bond appears to be linear. For the case of Cl−, a combination of linear and bridged forms, together with a competition between the solvation of the ion and hydrogen bonding among water molecules, are observed.
You have access to this article
Please wait while we load your content...
Something went wrong. Try again?