ACCURATE 2ND-ORDER CORRELATION ENERGIES OF HE AND BERYLLIUM

Very accurate second-order correlation energies for the ground states of He and Be are computed within the framework of the variational-perturbation method with HO=HHF. Particular attention is given to the problem of eliminating the radial basis saturation errors. The upper bounds to the second-order energies are -0.03736 and -0.7629 au respectively, which amount to 88.86 and 80.86% of the total correlation energies. A comparison with results obtained by several different methods is presented.