Translationally invariant clusters in coordinate space: an Euler-Lagrange approach

The authors have previously formulated a general translationally invariant version of the coupled cluster theory. The authors investigate the linearized approximation referred to as the second-order translationally invariant cluster method. In particular, they algebraically formulate and numerically solve this method at the optimal Euler-Lagrange level for finite bosonic systems. The method proves to be highly superior to the standard configuration-interaction calculations of the shell-model type, and confirms the validity of the Gaussian geminal expansion of the two-body cluster C₂.