Collect. Czech. Chem. Commun. 1997, 62, 829-842

Comparison of the Brillouin-Wigner Coupled Cluster Theory with the Standard Coupled Cluster Theory. Cancellation of Disconnected Terms in the Brillouin-Wigner Coupled Cluster Theory

Jozef Mášik and Ivan Hubač

Department of Chemical Physics, Faculty of Mathematics and Physics, Comenius University,842 15 Bratislava, Slovak Republic


In our article (Hubac I., Neogrady P.: Phys. Rev. A 50, 4558 (1994)) we have developed size-extensive Brillouin-Wigner coupled cluster (BWCC) theory. We have shown that the BWCC theory is fully equivalent to the standard coupled cluster theory. However, the BWCC theory does not obey the so-called linked cluster theorem. In this article we discuss the cancellation of disconnected terms in the BWCC theory.

Keywords: Brillouin-Wigner perturbation theory; Coupled clusters; Size consistency; Linked cluster theorem.