Configuration Interaction II: Correlation Energy and CSF's

This lecture delves into the calculation of correlation energy using Configuration Interaction methods, focusing on the contributions from doubles, triples, and quadruples, and the number of Configuration State Functions (CSF's) required for accurate results. The instructor discusses the importance of different levels of excitations and symmetries in limiting the number of determinants. Additionally, the lecture covers the significance of dynamic correlation and low-lying excited states in accurate electronic structure calculations, emphasizing the role of perturbation theory in handling electron correlation effects.