American Institute of Physics, The Journal of Chemical Physics, 12(144), p. 124513, 2016
DOI: 10.1063/1.4944613
Full text: Unavailable
The properties of halides from the lightest, Fuoride (F - ), to the heaviest, astatide (At - ), have been studied in water using a polarizable force-field approach based on molecular dynamics (MD) simulations at the 10 ns scale. The selected force-field explicitly treats the cooperativity within the halide-water hydrogen bond networks. The force- eld parameters have been adjusted to ab initio data on anion/water clusters computed at the relativistic Möller-Plesset second-order perturbation theory level of theory. The anion static polarizabilities of the two heaviest halides, I - and At - , were computed in the gas phase using large and diffuse atomic basis sets, and taking into account both electron correlation and spin-orbit coupling within a four-component framework. Our MD simulation results show the solvation properties of I - and At - in aqueous phase to be very close. For instance, their first hydration shells are structured and encompass 9.2 and 9.1 water molecules at about 3.70 ± 0.05 Å, respectively. These values have to be compared to the F - , Cl - , and Br - ones, i.e., 6.3, 8.4, and 9.0 water molecules at 2.74, 3.38, and 3.55 Å, respectively. Moreover our computations predict the solvation free energy of At - in liquid water at ambient conditions to be 68 kcal mol -1 , a value also close the I - one, about 70 kcal mol -1 . In all, our simulation results for I - are in excellent agreement with the latest neutron- and X-ray diffraction studies. Those for the At - ion are predictive, as no theoretical or experimental data are available to date.