title: The convergence of complete active space self-consistent-field configuration interaction including all single and double excitation energies to the complete basis set limit.
abstract: Examination of the convergence of full valence complete active space self-consistent-field configuration interaction including all single and double excitation (CASSCF-CISD) energies with expansion of the one-electron basis set reveals a pattern very similar to the convergence of single determinant energies. Calculations on the lowest four singlet states and the lowest four triplet states of N(2) with the sequence of n-tuple-zeta augmented polarized (nZaP) basis sets (n=2, 3, 4, 5, and 6) are used to establish the complete basis set limits. Full configuration-interaction (CI) and core electron contributions must be included for very accurate potential energy surfaces. However, a simple extrapolation scheme that has no adjustable parameters and requires nothing more demanding than CAS(10e(-),8orb)-CISD/3ZaP calculations gives the R(e), omega(e), omega(e)X(e), T(e), and D(e) for these eight states with rms errors of 0.0006 Angstrom, 4.43 cm(-1), 0.35 cm(-1), 0.063 eV, and 0.018 eV, respectively.
authors.affiliation: Hall-Atwater Laboratories of Chemistry, Wesleyan University, Middletown, Connecticut 06459-0180, USA.
authors.forename: George A
authors.initials: GA
authors.lastname: Petersson
authors.forename: David K
authors.initials: DK
authors.lastname: Malick
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Frisch
authors.forename: Matthew
authors.initials: M
authors.lastname: Braunstein