Bonding in the ClOO(2A″) and BrOO(2A″) radical: Nonrelativistic single-reference versus relativistic multi-reference descriptions in density functional theory
Abstract
The 2A″ state of ClOO and BrOO is investigated using single- and multi-reference DFT (density functional theory). Unrestricted DFT (UDFT) carried out with the BLYP functional exaggerates the ionic character of the X–OO bond (X = Cl, Br) and by this its bond dissociation energy, while UDFT with the B3LYP functional underestimates ionic character and bond dissociation energies. In previous investigations, this was overlooked and has led to a misleading interpretation of single determinant UDFT results for XOO(2A″). The correct description of the two radicals can only be achieved by an appropriate configurational state