Abstract
In this paper, we study stationary variant of extended coupled-cluster response approach for properties. This has been studied at the singles and doubles approximation using cubic-truncated functional. This approximation has been studied earlier around equilibrium for small molecules. In this paper, efficacy of this approximation has been shown using perturbative arguments. Further we have calculated dipole moments and polarizabilities of weakly interacting dimers of HF, H2O and H2O - HF complex. Results of HF and H2O monomers have been presented at the same level for comparison. The results have been compared with experimental results, wherever available and other theoretical results.
Highlights
Coupled-cluster (CC) method [1,2] is known to introduce dynamical correlation in an efficient manner through infinite partial summation of important terms of the many-body perturbation theory
We have shown that the double-linked extended coupled-cluster (ECC) functional is more appropriate compared to the XCC functional and produces fully size-extensive derivatives, in particular, the non-linear properties
Similar analysis is done for polarizability calculation to show the viability of cubic-ECC functional in singles and doubles approximation (ECCSD) method. We show that this cubic-ECCSD can describe dipole moments and polarizabilities of molecules possessing high dipole moments
Summary
Coupled-cluster (CC) method [1,2] is known to introduce dynamical correlation in an efficient manner through infinite partial summation of important terms of the many-body perturbation theory This method has been accepted as the method of choice for the calculation of energies and energy derivatives [3,4,5,6]. Using only one extra set of perturbation-independent variables, solved through a linear equation, the energy derivatives with respect to different modes of perturbation can be obtained [11] This Z-vector technique can be derived within the context of constrained variational method, as was done by Koch et al [12]. Pal and co-workers have pursued a fully stationary approach [13,14] based
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