An examination of intrinsic errors in electronic structure methods using the Environmental Molecular Sciences Laboratory computational results database and the Gaussian-2 set

The Gaussian-2 (G2) collection of atoms and molecules has been studied with Hartree–Fock and correlated levels of theory, ranging from second-order perturbation theory to coupled cluster theory with noniterative inclusion of triple excitations. By exploiting the systematic convergence properties of the correlation consistent family of basis sets, complete basis set limits were estimated for a large number of the G2 energetic properties. Deviations with respect to experimentally derived energy differences corresponding to rigid molecules were obtained for 15 basis set/method combinations, as well as the estimated complete basis set limit. The latter values are necessary for establishing the intrinsic error for each method. In order to perform this analysis, the information generated in the present study was combined with the results of many previous benchmark studies in an electronic database, where it is available for use by other software tools. Such tools can assist users of electronic structure codes in making appropriate basis set and method choices that will increase the likelihood of achieving their accuracy goals without wasteful expenditures of computer resources.