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
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.