Size Extensivity and Consistency in Quantum Chemistry

This lecture covers the concepts of size extensivity and consistency in quantum chemistry, explaining how properties scale with system size and remain constant. It also delves into post-Hartree-Fock methods like Configuration Interaction, Many-Body Perturbation Theory, and Coupled Cluster Theory. The slides detail the expansion of perturbed wavefunctions in doubly excited Slater determinants and the correction to energy levels, showcasing the importance of electron correlation in improving results.