Correlation consistent basis sets molecular benchmarks

In the present work, correlation consistent basis sets have been developed for the transition metal atoms Y and Hg using small-core quasirelativistic PPs, i.e., the ns and (nA)d valence electrons as well as the outer-core (nA)sp electrons are explicitly included in the calculations. This can greatly reduce the errors due to the PP approximation, and in particular the pseudo-orbitals in the valence region retain some nodal structure. Series of basis sets from double-through quintuple-zeta have been developed and are denoted as cc-pVwZ-PP (correlation consistent polarized valence with pseudopotentials). The methodology used in this work is described in Sec. II, while molecular benchmark calculations on YC, HgH, and Hg2 are given in Sec. III. Lastly, the results are summarized in Sec. IV. 

In our benchmark studies of correlated molecular calculations, we will focus largely on diatomic and triatomic molecules because, for these systems, it is possible to carry out calculations with the full range of correlation consistent basis sets. This allows us to establish definitively the complete basis set limits of the properties of interest, i.e., Only... 

The basis set requirements needed to accurately compute the core-core correlation is rather severe. Molecular calculations indicate that the basis set requirements to obtain the core-valence contribution are somewhat less stringent, but the basis set requirements are not well defined. The core-valence correlation consistent basis sets of Woon and Dunning should help benchmark the basis set requirements as they provide sets which are systematically expandable. 

Peterson KA, Yousaf KE. Molecular core-valence correlation effects involving the post-d elements Ga-Rn Benchmarks and new pseudopotential-based correlation consistent basis sets. J Chem Phys. 2010 133 174116. 

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