A COUPLED-CLUSTER STUDY OF THE ELECTRON-AFFINITY OF THE OXYGEN ATOM

Despite quantum chemists' best efforts, a highly accurate ab initio prediction of the electron affinity of atomic oxygen has remained elusive. In this study the coupled cluster method including all single, double, and perturbative triple excitations [CCSD(T)] is employed in conjunction with very large uncontracted Gaussian basis sets. A systematic shell-by-shell optimization at this level of theory leads to an optimal 23s26p1Od5f3g basis set. Second-order configuration interaction (SOCI) calculations are also carried out and the coupled cluster results are found to be in good agreement with them. Our best theoretical prediction (1.415 eV) is 0.047 eV smaller than the experimental result but still marks a substantial improvement over previous high-quality calculations. The potential sources of error in our predictions are discussed.