As a further development of the previously introduced a posteriori Universal State-Selective (USS) corrections [K. Kowalski, J. Chem. Phys. 134, 194107 (2011)] and [Brabec et al., J. Chem. Phys., 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 FCI limit is also investigated. Various forms of the USS and simplified diagonal USSD corrections at the SD and SD(T) 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 BWCC 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.
Revised: May 22, 2015 |
Published: March 17, 2015
Citation
Banik S., L. Ravichandran, J. Brabec, I. Hubac, K. Kowalski, and J. Pittner. 2015.Iterative universal state selective correction for the Brillouin-Wigner multireference coupled-cluster theory.Journal of Chemical Physics 142, no. 15:Article No. 114106.PNNL-SA-107175.doi:10.1063/1.4914311