Gaussian basis sets for use in correlated molecular calculations .6. Sextuple zeta correlation consistent basis sets for boron through neon

The family of correlation consistent polarized valence basis sets (cc-pVXZ) has been extended to include sextuple zeta sets (cc-pV6Z) for the atoms boron through neon. Potential energy functions have been calculated with these sets for the electronic ground states of N-2 and HF using a number of correlated wave functions: MP2, MP3, MP4, CCSD, CCSD(T) and CAS+1+2. Spectroscopic constants have been calculated for each level of theory and have been compared with experiment. Combining these results with those of prior studies, complete basis set limits have been estimated for E(e), D-e and r(e). It is found that the cc-pV6Z basis sets yield dissociation energies that are within 0.6-0.8 kcal mol(-1) (N-2) and 0.1 kcal mol(-1) (HF) of the estimated CBS limits. Adding core-core and core-valence contributions to the CCSD(T) CBS limits yields D-e's that are within 0.1 kcal mol(-1) of the experimental values.