CC3 triplet excitation energies using an explicit spin coupled excitation space

Triplet excitation energies are derived in the approximate triples model CC3 using an explicit spin coupled triplet excitation space. The explicit spin coupled excitation space gives considerable computational savings compared to the spin–orbital approach. Sample calculations are performed on the Be2 and CH2 systems and the performance of the CC3 results are evaluated from a comparison with full configuration interaction (FCI) results.

[1]  P. Piecuch,et al.  The state-universal multi-reference coupled-cluster theory with perturbative description of core-virtual excitations , 2001 .

[2]  P. Jørgensen,et al.  Triplet excitation energies in the coupled cluster singles and doubles model using an explicit triplet spin coupled excitation space , 2000 .

[3]  Linear response CC2 triplet excitation energies , 2000 .

[4]  P. Jørgensen,et al.  Singlet excited states of Be2 , 2000 .

[5]  M. Ratner.  Molecular electronic-structure theory , 2000 .

[6]  V. Bondybey,et al.  Electronic structure of Be2: theoretical and experimental results , 1999 .

[7]  H. Schaefer,et al.  Structures and vibrational frequencies in the full configuration interaction limit: Predictions for four electronic states of methylene using a triple-zeta plus double polarization (TZ2P) basis , 1998 .

[8]  H. Schaefer,et al.  Full configuration interaction benchmarks for the states of methylene , 1997 .

[9]  H. Schaefer,et al.  The 3d Rydberg (3A2) electronic state observed by Herzberg and Shoosmith for methylene , 1997 .

[10]  Trygve Helgaker,et al.  The CC3 model: An iterative coupled cluster approach including connected triples , 1997 .

[11]  Péter G. Szalay,et al.  High-quality theoretical potential energy surface for Be2 by using the multireference averaged quadratic coupled-cluster (MR-AQCC) method and large basis sets , 1996 .

[12]  Poul Jørgensen,et al.  Perturbative triple excitation corrections to coupled cluster singles and doubles excitation energies , 1996 .

[13]  J. Olsen,et al.  Excitation energies of H2O, N2 and C2 in full configuration interaction and coupled cluster theory , 1996 .

[14]  P. Bruna,et al.  Strongly bound doubly excited states of Be2 , 1996 .

[15]  N. Handy,et al.  Dynamical and Nondynamical Correlation , 1996 .

[16]  Ove Christiansen,et al.  Response functions in the CC3 iterative triple excitation model , 1995 .

[17]  Jeppe Olsen,et al.  Excitation energies of BH, CH2 and Ne in full configuration interaction and the hierarchy CCS, CC2, CCSD and CC3 of coupled cluster models , 1995 .

[18]  Poul Jørgensen,et al.  The second-order approximate coupled cluster singles and doubles model CC2 , 1995 .

[19]  R. Bartlett,et al.  On the singlet–triplet separation in methylene: A critical comparison of single‐ versus two‐determinant (generalized valence bond) coupled cluster theory , 1995 .

[20]  John D. Watts,et al.  Economical triple excitation equation-of-motion coupled-cluster methods for excitation energies , 1995 .

[21]  Josef Paldus,et al.  Orthogonally spin‐adapted state‐universal coupled‐cluster formalism: Implementation of the complete two‐reference theory including cubic and quartic coupling terms , 1994 .

[22]  R. Bartlett,et al.  The inclusion of connected triple excitations in the equation‐of‐motion coupled‐cluster method , 1994 .

[23]  L. Gagliardi,et al.  Full configuration interaction calculations on Be2 , 1994 .

[24]  John F. Stanton,et al.  The equation of motion coupled‐cluster method. A systematic biorthogonal approach to molecular excitation energies, transition probabilities, and excited state properties , 1993 .

[25]  Nicholas C. Handy,et al.  A study of O3, S3, CH2, and Be2 using Kohn–Sham theory with accurate quadrature and large basis sets , 1993 .

[26]  Wim Klopper,et al.  CC-R12, a correlation cusp corrected coupled-cluster method with a pilot application to the Be2 potential curve , 1992 .

[27]  T. Dunning,et al.  Electron affinities of the first‐row atoms revisited. Systematic basis sets and wave functions , 1992 .

[28]  John D. Watts,et al.  Non-iterative fifth-order triple and quadruple excitation energy corrections in correlated methods , 1990 .

[29]  T. H. Dunning.  Gaussian basis sets for use in correlated molecular calculations. I. The atoms boron through neon and hydrogen , 1989 .

[30]  O. Strausz,et al.  Ab initio molecular orbital studies of the potential energy curves for the low lying triplet states of Be2 and Be3 , 1988 .

[31]  Y. Öhrn,et al.  Calculation of spectroscopic properties of the ground and excited states of Be2 according to the antisymmetrized geminal power (AGP) based excitation propagator , 1985 .