The multi-reference Hilbert space coupled-cluster study of the Li2 molecule. Application in a complete model space

Abstract The ground and three low-lying excited states of the Li 2 molecule are studied by our new multi-reference fully quadratic Hilbert space coupled-cluster method, using a complete model space of four reference functions. DZ and DZP results are reported and compared with full-Cl. The deviations are usually within the range of a few tenths of microhenry. Questions of convergence, including the modification of the one-electron potential and its critical influence on the computational performance of the present method are discussed.

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