Equations of motion coupled clusters

Stanton JF, Bartlett RJ (1993) The equation of motion coupled-cluster method - a systematic biorthogonal approach to molecular-excitation energies, transition-probabilities, and excited-state properties. J Chem Phys 98 7029... 

Krylov AI (2006) Spin-flip equation-of-motion coupled-cluster electronic structure method for a description of excited states, bond breaking, diradicals, and triradicals. Acc Chem Res 39 83-91... 

The vertical IPs of CO deserve special attention because carbon monoxide is a reference compound for the application of photoelectron spectroscopy (PES) to the study of adsorption of gases on metallic surfaces. Hence, the IP of free CO is well-known and has been very accurately measured [62]. A number of very efficient theoretical methods specially devoted to the calculation of ionization energies can be found in the literature. Most of these are related to the so-called random phase approximation (RPA) [63]. The most common formulations result in the equation-of-motion coupled-cluster (EOM-CC) equations [59] and the one-particle Green s function equations [64,65] or similar formalisms [65,66]. These are powerful ways of dealing with IP calculations because the ionization energies are directly obtained as roots of the equations, and the repolarization or relaxation of the MOs upon ionization is implicitly taken into account [59]. In the present work we remain close to the Cl procedures so that a separate calculation is required for each state of the cation and of the ground state of the neutral to obtain the IP values. 

S. Hirata, M. Nooijen, I. Grabowski, and R. J. Bartlett, Perturbative corrections to coupled-cluster and equation-of-motion coupled-cluster energies a determinantal analysis. J. Chem. Phys. 114, 3919 (2001). 

BASIC ELEMENTS OF COUPLED-CLUSTER AND EQUATION-OF-MOTION COUPLED-CLUSTER METHODS... 

Inclusion of connected triple excitations in the equation-of-motion coupled-cluster method for calculating excitation energies was also tested on SiFP230. Excitation energies predicted for the lowest triplet state and the two lowest excited singlet states 1 Si and 2 lAi were within a kcal mol 1 of the predictions of the full Cl calculation when triple excitations were included, but only for the 2 3Ai state was there marked improvement over the inclusion of only single and double excitations. 

J. Geersten, M. Rittby, R.J. Bartlett, The equation-of-motion coupled-cluster method Excitation energies of Be and CO, Chem. Phys. Lett. 164 (1989) 57 D.C. Comeau, R.J. Bartlett, The equation-of-motion coupled-cluster method. Applications to open- and closed-shell reference states, Chem. Phys. Lett. 207 (1993) 414. 

M. Nooijen and R. J. Bartlett,/. Chem. Phys., 107, 6812 (1997). Similarity-Transformed Equation-of-Motion Coupled-Cluster Theory Details, Examples, And Comparisons. 

In two recent publications we have tried to characterize the excited state properties of 1 and 3 in order to facilitate their detection by LIF-spectroscopy. Our main tool in this effort has been equation of motion coupled cluster theory (EOM-CC). The EOM-CCSD method, which is equivalent to linear response CCSD, has been shown to provide an accurate description of both valence and excited states even in systems where electron correlation effects play an important role [39]. Computed transition energies for excitations that are of mainly single substitution character are generally accurate to within 0.1 eV. We have found the EOM-CCSD method to perform particularly well in combination with the doubly-augmented cc-pVDZ (d-aug-cc-pVDZ) basis set. This basis seems to provide equally balanced descriptions of ground and excited states,... 

M. Nooijen, J.G. Snijders, Int. J. Quantum Chem. 48 (1993) 15. For ionization potentials, equation-of-motion coupled-cluster, coupled-cluster linear response theory,... 

More demanding calculations conducted by Daniel et al. using equations-of-motion coupled cluster methods (EOM-CC) provided a better description of the contribution of MLCT andMC transitions to the electronic spectrum of Cr(CO)6 [13]. These calculations confirm that the lowest-energy transition, which is responsible for the shoulder on the low-energy side of the first absorption maximum, corresponds to... 

There are several single reference methods to compute electronic transition energies. Among them are configuration interaction-singles (CIS) [48], random-phase approximation (RPA) [49, 50], equation-of-motion couple cluster (EOMCC)... 

Equation-of-Motion Coupled-Cluster Theory, Excitons... 

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.,... 

Equation-of-motion coupled-cluster singles, doubles,... 

Abstract This chapter presents a review of equation-of-motion coupled-cluster (EOM-CC) and... 

Watts JD, Bartlett RJ (1995) Economical triple excitation equation-of-motion coupled-cluster methods for excitation energies. Chem Phys Lett 233 81-87. 

Kowalski K, Piecuch P (2000) The active-space equation-of-motion coupled-cluster methods for excited states The EOMCCSDt approach. J Chem Phys 113 8490-8502. 

Hirata S, Nooijen M, Bartlett RJ (2000) High-order determinantal equation-of-motion coupled-cluster calculations for electronic excited states. Chem Phys Lett 326 255—262. 

---