The importance of self-interaction and nonlocal exchange corrections to the density functional theory of intracavity electrons in Na-doped sodalites

Electrons that are confined to zeolite cavities are modeled using a simplif ied pseudopotential scheme to represent the interaction of the electrons wi th both the sodalite framework and the Na+ ions. By comparing theory with r ecent experimental studies of G centers in Na-doped NaBr-SOD it is demonstr ated that restricted forms of density functional theory, where two electron s are forced to pair in the same Kohn-Sham orbital, fail to correctly predi ct the true nature of the singlet, (spin unpolarized!, G center. Electron c onfinement leads to generalized gradient corrections to the exchange of 0.7 4 eV and self-interaction corrections (SIC) of 0.7 eV over calculations per formed in the local spin density approximation (LSDA). Only the self-intera ction corrected generalized gradient approximation and the unrestricted Har tree-Fock approximation are in accord with experiment for the relative stab ility of the triplet (spin polarized) state. The unrestricted Hartree-Fock method is used to show that G-center absorptions will be blueshifted with r espect to absorptions due to the isolated F centers. Constructing a Hubbard Hamiltonian we show that the exchange coupling ranges in values from 2.3 m eV (UHF) to 3.6 meV(SIC-LSDA) corresponding to Neel temperatures that range from 27 to 41 K in agreement with experiment. (C) 1999 American Institute of Physics. [S0021-9606(99)00615-7].