Extensions and applications of symmetry-adapted perturbation theory

Symmetry-Adapted Perturbation Theory (SAPT) provides a reliable method for ab initio calculations of intermolecular interaction energies. This methodology has been extended by including coupled-cluster single and double excitations in the calculation of the second-order polarization energy. The second-order dispersion energy at the double excitation level has been implemented and the importance of this term has been demonstrated with suitable example systems. Another development was a demonstration that the SAPT intermolecular interaction energy components can be calculated in a significantly restricted basis with no penalty in the accuracy of these components. Finally, two important systems, He...