Fermi-Lowdin orbital self-interaction corrections applied to water clusters: Polarizabilities, dipole moments, and ionization energies*

The self-interaction (SI) error in density functional approximations (DFA) often leads to excessive delocalization of electron density. We examine the effect of self-interaction correction on the static dipole polarizabilities of small water clusters (H2O)n for n=1-6 using the Fermi-Lowdin self-interaction correction (FLOSIC) method. The static polarizability of a molecule determines its response to an applied static electric field. Density functional approximations generally overestimate the polarizabilities of molecules and atoms which is found to be improved by incorporation of SI correction. The polarizabilities of the water clusters are calculated with DFAs at the local, generalized gradient and meta-GGA levels. Previously optimized geometries at the CCSD(T) level are used for this calculation. Results show that the lower level approximations, LDA and GGA, overestimate the polarizability values whereas FLOSIC corrects the polarizabilities leading to better agreement with reference CCSD(T) values. We also investigate the effect of removing the self-interaction error on the dipole moments and ionization potentials of these clusters with different functionals. The results will be presented and discussed.