In an earlier paper by the authors, the focus lay on using the Gn methods proposed by Curtiss et al. These methods fall under the umbrella of hybrid methods. Hybrid methods determine the energies of molecules at their equilibrium geometries by combining results obtained from highlevel correlation methods (like quadratic configuration interaction theory (QCISD) and coupled cluster theory (CCSD)) using small atomic orbital basis sets with results from lower level methods (like MP2 and MP4) using a large basis set. To increase the accuracy of the final result, an empirical additive correction term is determined as follows. For a large test set of small molecules, a specific property(e.g., atomization energy) is computed using a particular hybrid method and compared with reference values based on experiment. The empirical term is the correction factor that brings the test set results into the best overall agreement with the experimental data.