Coupled cluster singles and doubles theory

However, until today no systematic comparison of methods based on MpUer-Plesset perturbation (MP) and Coupled Cluster theory, the SOPPA or multiconfigurational linear response theory has been presented. The present study is a first attempt to remedy this situation. Calculations of the rotational g factor of HF, H2O, NH3 and CH4 were carried out at the level of Hartree-Fock (SCF) and multiconfigurational Hartree-Fock (MCSCF) linear response theory, the SOPPA and SOPPA(CCSD) [40], MpUer-Plesset perturbation theory to second (MP2), third (MP3) and fourth order without the triples contributions (MP4SDQ) and finally coupled cluster singles and doubles theory. The same basis sets and geometries were employed in all calculations for a given molecule. The results obtained with the different methods are therefore for the first time direct comparable and consistent conclusions about the performance of the different methods can be made. 

The single-reference coupled cluster (CC) theory [1-5] has become a standard computational tool for studying ground-state molecular properties [6-10]. The basic approximations, such as CCSD (coupled cluster singles and doubles approach) [11-15], and the noniterative CCSD[T] [16,17] and CCSD(T) [18] methods, in which the cleverly designed corrections due to... 

Koch H, Jdrgen H, Jensen A, Jorgensen P, Helgaker T, Scuseria GE, Schaefer III HF (1990) Coupled cluster energy derivatives. Analytic Hessian for the closed-shell coupled cluster singles and doubles wave function Theory and applications. J Chem Phys 92 4924-4940... 

The partitioned equation-of-motion second-order many-body perturbation theory [P-EOM-MBPT(2)] [67] is an approximation to equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) [17], which will be fully described in Section 2.4. The EOM-CCSD method diagonalizes the coupled-cluster effective Hamiltonian H = [HeTl+T2) in the singles and doubles space, i.e.,... 

H. Koch, H. J. Aa. Jensen, P. j0rgensen, T. Helgaker, G. E. Scuseria, and H. F. Schaefer, /. Chem. Phys., 92, 4924 (1990). Coupled-Cluster Energy Derivatives. Analytic Hessian for the Closed-Shell Coupled-Cluster Singles and Doubles Wave Functions Theory and Applications. 

T. D. Crawford, Ph.D. Thesis, University of Georgia, 1996. Many-Body Perturbation Theory and Perturbational Triple Excitation Corrections to the Coupled-Cluster Singles and Doubles Method for High-Spin Open-Shell Systems. 

Again the terms to be included were based on a perturbation order argument.6,16 The contribution of connected triples was shown numerically to be not inconsequential in applications of perturbation theory.19,20 More recently, Purvis and Bartlett16 reported the equations and initial implementation of a full coupled-cluster singles and doubles model (CCSD) this theory includes all terms in the first five parentheses, C0-C4, of Eq. (6) except for Ti, r4, and T Ti. The inclusion of disconnected terms is known to enhance the numerical stability of the coupled equations.21,22... 

SM calculations are broadly based on either the (i) Hartree-Fock method (ii) Post-Hartree-Fock methods like the Mpller-Plesset level of theory (MP), configuration interaction (Cl), complete active space self-consistent field (CASSCF), coupled cluster singles and doubles (CCSD) or (iii) methods based on DFT [24-27]. Since the inclusion of electron correlation is vital to obtain an accurate description of nearly all the calculated properties, it is desirable that SM calculations are carried out at either the second-order Mpller-Plesset (MP2) or the coupled cluster with single, double, and perturbative triple substitutions (CCSD(T)) levels using basis sets composed of both diffuse and polarization functions. 

CASPT2 complete aetive spaee based second-order perturbation theory CCSD coupled-cluster single and double CCSD(T) CCSD corrected with triple excitations Cl configmation interaction... 

Coupled cluster theory Coupled cluster theory has been employed for calculations of the spin-spin coupling constants by Perera, Sekino and Bartlett 52.53 They have derived the indirect spin-spin coupling constant as a derivative of the coupled cluster singles and doubles (CCSD) energy (see... 

Janowskl, T, Ford, A. R., and Pulay, P. (2007). Parallel calculation of coupled cluster singles and doubles wave functions using array files, / Chem. Theory Comput 3, pp. 1368-1377, doi 10.1021/ct700048u. 

Pedersen, T. B., Sanchez de Meras, A. M.and Koch, H. (2004). Polarizability and optical rotation calculated from the approximate coupled cluster singles and doubles CC2 linear response theory using Cholesky decompositions, /. Chem. Phys. 120, pp. 8887-8897, doiilO.1063/1. 1705575. 

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