The composite method of symmetry adapted perturbation theory

In symmetry-adapted perturbation theory (SAPT), accurate calculations on non-covalent interaction for large complexes with more than 50 atoms are impractical using a large basis set. The more efficient with a smaller basis set, however, usually results in poor prediction in terms of dispersion and overall energies. In this study, we propose a composite method with a baseline calculated at SAPT2/aug-cc-pVTZ with dispersion term corrected at SAPT2+ level with a smaller basis set at the canonical limit using extrapolation techniques. Two point and three point extrapolation schemes are discussed, and we showed that our composite methods perform better than the previously ranked silver standard and can even compete with gold standard with the computational cost in between the latter and former's.