Brueckner coupled cluster doubles

C. D. Sherrill, A. I. Krylov, E. F. C. Byrd, and M. Head-Gordon, /. Chem. Phys., 109, 4171 (1998). Energies and Analytic Gradients for a Coupled-Cluster Doubles Model Using Variational Brueckner Orbitals. Application to Symmetry Breaking in O4. [Pg.134]

B-CC = Brueckner CC CCD = coupled-cluster doubles CCSD = coupled-cluster singles and doubles CCSDT = coupled-cluster singles, doubles, and triples CCSDTQ = coupled-cluster singles, doubles, triples, and quadruples Cl = configuration interaction EOM = equation-on-motion FCI = full-configuration interaction. [Pg.615]

Another approach of this kind uses the approximate Brueckner orbitals from a so-called Brueckner doubles, coupled-cluster calculation [39, 40]. Methods of this kind are distinguished by their versatility and have been applied to valence ionization energies of closed-shell molecules, electron detachment energies of highly correlated anions, core ionization... [Pg.140]

The correlation treatments were done at the levels of second order perturbation theory, coupled cluster theory with single and double substitutions (CCSD) [55 59], an approximate form of CCSD, and that form with Brueckner orbitals (BO) [102], The approximate form [103,104], using herein the designation ACCSD or ACCD, has been shown to yield potential curves, potential surface slices, and properties very close to the corresponding CC results [104 106],... [Pg.19]

The PCM coupled-cluster theory has been presented at the coupled-cluster single and double (CCSD) excitation level approximation [9, 11], at the Brueckner doubles (BD) coupled-cluster level [12], and within the symmetry adapted cluster (SAC) method [10]. [Pg.24]

BD(T) = Brueckner doubles CCSD(T) = coupled cluster HLC = higher-level correction QCISD(T) = quadratic configuration interaction. [Pg.1104]

For correlated methods such as truncated configuration interaction (CID or CISD), coupled cluster (CCD or CCSD), quadratic configuration interaction (QCISD) and Brueckner doubles (BD) (see Configuration Interaction and Coupled-cbister Theory), the energy and wavefunction can be written as... [Pg.2667]

Chapter 13 discusses coupled-cluster theory. Important concepts such as connected and disconnected clusters, the exponential ansatz, and size-extensivity are discussed the Unked and unlinked equations of coupled-clustCT theory are compared and the optimization of the wave function is described. Brueckner theory and orbital-optimized coupled-cluster theory are also discussed, as are the coupled-cluster variational Lagrangian and the equation-of-motion coupled-cluster model. A large section is devoted to the coupled-cluster singles-and-doubles (CCSD) model, whose working equations are derived in detail. A discussion of a spin-restricted open-shell formalism concludes the chapter. [Pg.546]