Iterative universal state selective correction for the Brillouin-Wigner multireference coupled-cluster theory.

Abstract

As a further development of the previously introduced a posteriori Universal State-Selective (USS) corrections [K. Kowalski, J. Chem. Phys. 134, 194107 (2011); J. Brabec et al., ibid. 136, 124102 (2012)], we suggest an iterative form of the USS correction by means of correcting effective Hamiltonian matrix elements. We also formulate USS corrections via the left Bloch equations. The convergence of the USS corrections with excitation level towards the full configuration interaction (FCI) limit is also investigated. Various forms of the USS and simplified diagonal USS corrections at the singles and doubles and perturbative triple levels are numerically assessed on several model systems and on the ozone and tetramethyleneethane molecules. It is shown that the iterative USS correction can successfully replace the previously developed a posteriori Brillouin-Wigner coupled cluster size-extensivity correction, while it is not sensitive to intruder states and performs well also in other cases when the a posteriori one fails, like, e.g., for the asymmetric vibration mode of ozone.

DOI: 10.1063/1.4914311

Cite this paper

@article{Banik2015IterativeUS, title={Iterative universal state selective correction for the Brillouin-Wigner multireference coupled-cluster theory.}, author={Subrata Banik and Lalitha Ravichandran and Jiri Brabec and Ivan Huba{\vc} and Karol Kowalski and Jiř{\'i} Pittner}, journal={The Journal of chemical physics}, year={2015}, volume={142 11}, pages={114106} }