An ab initio study of the Cj cation using multireference methods

The energy difference between the linear S+ and cyclic £?2 structures of G$ has been investigated using large [5s3p2dlf] basis sets and multireference electron correlation treatments, including complete active space SCF (CASSCF), multireference CI (MRCI), and averaged coupled-pair functional (ACPF) methods, as well as the single-reference quadratic configuration interaction (QCISD(T)) method. Our best estimate, including a correction for basis set incompleteness, is that the linear form lies above the cyclic form by 5.2+i;o kcal/mol. The E+ state is probably not a transition state, but a local minimum. Reliable computation of the cyclic/linear energy difference in C$ is extremely demanding of the electron correlation treatment used: of the singlereference methods previously considered, CCSD(T) and QCISD(T) perform best. The MRCI+Q(0.01)/[4s2pld] energy separation of 1.68 kcal/mol should provide a comparison standard for other electron correlation methods applied to this system. failing address: NASA Ames Research Center, Moffett Field, CA 94035-1000 (NASA-CR-189026) AN AB INITIO STUDY OF THE N92-21401 C3(+) CATION USING MULTIREFERENCE METHODS (Eloret Corp.) 19 p CSCL 20H Unclas G3/72 0052235 https://ntrs.nasa.gov/search.jsp?R=19920012158 2018-04-03T19:00:25+00:00Z