Spin-component scaled coupled-clusters singles and doubles optimized towards calculation of noncovalent interactions.

The same- and opposite-spin scaling parameters for the SCS-CCSD method were reparametrized on the basis of benchmark CCSD(T)/CBS set interaction energies from the S22 set. New parameters were close to the original ones but swap between the different spin components, being 1.11 for the opposite- and 1.28 for the same-spin component. The RMSD, and especially, the largest error for the S22 were significantly reduced in comparison with the original parametrization. These statistical factors were only slightly worse when the S22x5 test set, containing not only the equilibrium but also the non-equilibrium geometries, was used. This new method, named the SCS(MI)-CCSD ("MI" stands for "Molecular Interactions") can thus be recommended for highly accurate calculations of interaction energies of various noncovalent interaction types, for which the CCSD(T)/CBS calculations are impractical.