Coupled-cluster calculations using local potentials -: art. no. 012504

Coupled-cluster calculations starting from exchange-only local-density approximation (XLDA), Krieger-Li-Iafrate (KLI), and Kohn-Sham (KS) wave functions are compared with those using the Hartree-Fock (HF) determinant as a reference. The total energies are found to be close, the difference being maximally 2 mhartree in the systems studied (the first terms in the He, Be, Ne, Mg, Ar isoelectronic series). The convergence is, however, sensitive to the choice of the reference: KLI and KS converge, in general, faster than HF in spite of being a worse approximation in the first two orders of perturbation theory. The improvement of convergence due to the use of the KLI or KS references is more pronounced in the systems showing near degeneracy, such as in the Be series. For XLDA, the convergence properties are either comparable to those of KLI or oscillatory, depending on the system. In a second part, the numerical results are analyzed (in the HF and KLI cases) by using first-order developments with respect to nuclear charge Z at large Z.