Journal of Physical Chemistry A, Vol.122, No.13, 3413-3422, 2018
Structures and Spectroscopic Properties of F-(H2O)(n) with n=1-10 Clusters from a Global Search Based On Density Functional Theory
Using a genetic algorithm incorporated in density functional theory, we explore the ground state structures of fluoride anion-water clusters F-(H2O) with n = 1-10. The F-(H2O) clusters prefer structures in which the F- anion remains at the surface of the structure and coordinates with four water molecules, as the F-(H2O) clusters have strong F--H2O interactions as well as strong hydrogen bonds between H2O molecules. The strong interaction between the F- anion and adjacent H2O molecule leads to a longer O-H distance in the adjacent molecule than in an individual water molecule. The simulated infrared (IR) spectra of the F-(H2O)(1-5) clusters obtained via second-order vibrational perturbation theory (VPT2) and including anharmonic effects reproduce the experimental results quite well. The strong interaction between the F- anion and water molecules results in a large redshift (600-2300 cm(-1)) of the adjacent O-H stretching mode. Natural bond orbital (NBO) analysis of the lowest-energy structures of the F-(H2O)(1-10) clusters illustrates that charge transfer from the lone pair electron orbital of F- to the antibonding orbital of the adjacent O-H is mainly responsible for the strong interaction between the F- anion and water molecules, which leads to distinctly different geometric and vibrational properties compared with neutral water clusters.