Structures and vertical detachment energies of water cluster anions (H2O)−n with n = 6–11

Abstract

The structures and vertical detachment energies (VDEs) of water cluster anions (H2O)− with n = 6–11 are examined by an unbiased global search algorithm, namely comprehensive genetic algorithm (CGA) combined with density functional theory. Benchmark evaluation shows that the B3LYP-D3/6-31(+,3+)G* level of theory could give comparable accuracy of MP2/6-31(+,3 +)G* about the geometric property of water cluster anions. Meanwhile, the energies simulated at the MP2/6-31(+,3 +)G* level of theory converge to the results of CCSD(T)/6-31(+,3 +)G* level. Therefore, the relative energies and VDE of water cluster anions are calculated at the MP2/6-31(+,3 +)G*//B3LYP-D3/6-31(+,3 +)G* level of theory. The structures of (H2O)6–11− clusters obtained from CGA represent that the excess electron destroys the hydrogen bond network and forms an electron hole in most structures. The water cluster anions prefer to form three-membered rings and four-membered rings. As the cluster size increases, the VDE of the water cluster anions increases because the excess electron becomes less diffuse in the larger-sized clusters. Our work gives a comprehensive study about the excess electron disturbing the small-sized neutral water clusters.