Coupled cluster singles and doubles approach

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... 

T. D. Crawford and H. F. Schaefer,/. Chem. Phys., 104, 6259 (1996). A Comparison of Two Approaches to Perturbational Triple Excitation Corrections to the Coupled-Cluster Singles and Doubles Method for High-Spin Open-Shell Systems. 

The purpose of the present work is to test the efficiency and performance of the implementation of the explicitly correlated coupled-cluster singles-and-doubles, CCSD(F12), model in the Turbomole package. This model, initially proposed by Fliegl et al. [41], is the approximation to the full CCSD-F12 approach originally given by Noga et al [40]. It has been demonstrated that this method is able to recover quintuple- quality correlation energies with the orbital basis set of the size of triple- [31]. 

Relativistic calculations of NMR properties of RgH ion (where Rg = Ne, Ar, Kr, Xe), Pt shielding in platinum complexes, and Pb shielding in solid ionic lead(II) halides have been reported in this review period. For the Rg nucleus in the RgH ions, the following methods were used and results compared with each other non-relativistic uncorrelated method (HF), relativistic uncorrelated methods, four component Dirac Hartree-Fock method (DHF) and two-component zeroth order regular approach (ZORA), non-relativistic correlated methods using second order polarization propagator approach SOPPA(CCSD), SOPPA(MP2), respectively coupled cluster singles and doubles or second order Moller-Plesset, and... 

There is nowadays agreement that the most systematic approach to the solution of the electronic Schrodinger equation is provided by coupled-cluster theory. The coupled-cluster singles and doubles scheme with noniterative treatment of triply excited clusters, CCSD(T), " is sometimes addressed as the gold standard in quantum chemistry, and recent efforts to facilitate calculations with higher-order methods have enabled the solution of the electronic Schrodinger equation with unprecedented accuracy. 

The EOM-CCSD method has been shown to be an accurate approach for calculating excitation energies (EE-) (29,30), electron affinities (EA-) (31), and ionization potentials (IP-) (32) of closed-shell systems. For the computations presented here, a coupled-cluster singles and doubles (CCSD) calculation is first performed on the closed-shell NO3" anion system. The Hamiltonian is similarity... 

CCSD(T) Coupled cluster approach with single and double substitutions and inclusion... 

However, due to the availability of numerous techniques, it is important to point out here the differences and equivalence between schemes. To summarize, two EDA families can be applied to force field parametrization. The first EDA type of approach is labelled SAPT (Symmetry Adapted Perturbation Theory). It uses non orthogonal orbitals and recomputes the total interaction upon perturbation theory. As computations can be performed up to the Coupled-Cluster Singles Doubles (CCSD) level, SAPT can be seen as a reference method. However, due to the cost of the use of non-orthogonal molecular orbitals, pure SAPT approaches remain limited... 

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