Optimized Structural Data at the Complete Basis Set Limit via Successive Quadratic Minimizations

Two variants of a successive quadratic minimization method (SQM and c-SQM) are suggested to calculate the structural properties of molecular systems at the complete basis set (CBS) limit. When applied to H-3(+), H2O, CH2O, SH2, and SO2, they revealed CBS/(x(1), x(2)) structural parameters that significantly surpass the raw ones calculated at the x(2) basis set level. Such a performance has also been verified for the intricate case of the water dimer. Because the c-SQM method is system specific, thus showing somewhat enhanced results relative to the general SQM protocol, it can be of higher cost depending on the level of calibration used. Yet, it hardly surpasses the general quality of the results obtained with the cost-effective SQM method. Since the number of cycles required to reach convergence is relatively small, both schemes are simple to use and easily adaptable to any of the existing extrapolation schemes for the Hartree-Fock and correlation energies.

Automated summary

Two successive quadratic minimization methods, SQM and c-SQM, are suggested for calculating structural properties of molecular systems at the complete basis set (CBS) limit. The c-SQM method shows somewhat enhanced results compared to the general SQM protocol, but at a higher cost. Both methods are simple to use and easily adaptable to existing extrapolation schemes for Hartree-Fock and correlation energies.