Single-point energy corrections were calculated for cuts of potential energy surfaces where local or global minima are located for each test system. In most cases, the distance was measured between two chosen atoms from each monomer, except for the ethylene dimer, where the distance is simply the separation between the parallel molecular planes. For convenience, in this paper, we give distances as the multiple of the equilibrium distance R e . To determine the values of the equilibrium distances R e , we optimized intermolecular interaction energies in selected complexes using the coupled-cluster singles and doubles (CCSD) method com-FIG. . Absolute relative errors of the first and second-order exchange energies calculated in the S 2 and S 4 approximations for the Be-NH 3 shown as a function of the Be-N distance. The calculations were performed using the jun-cc-pVTZ basis set. The equilibrium distances for the selected test systems are presented in the Table .