Coupled-cluster based basis sets for valence correlation calculations. New primitives, frozen atomic natural orbitals, and basis sets from double to hextuple zeta for atoms H, He, and B-Ne.

Abstract

A series of new basis sets generated from coupled-cluster theory are presented. Sets of primitive Gaussians for angular momentum shells containing occupied orbitals are optimized and extended until the Hartree-Fock energy improvement per electron falls below 10 μH. This same energy threshold is applied to the energy from the coupled-cluster singles, doubles, and perturbative triples (CCSD(T)) approximation and taken as a guide to the generation of sets of polarization functions, constructed at the level of second-order many-body perturbation theory, once it is shown that practically indistinguishable results are obtained if the more costly CCSD(T) approach is used. A variant of the usual atomic natural orbitals (ANOs) grounded on the frozen natural orbital idea is explored, leading to the frozen ANO (FANO) contraction scheme, whose truncation pattern and convergence capabilities are thoroughly tested. Due to its superior description of the single determinant solution, the FANOs are proposed as the recommended contraction approach. FANO basis sets of sizes ranging from double to hextuple zeta are provided for atoms H through Ne and examined in atomic and molecular calculations.