CI Continued/Many-Body Perturbation Theory

This lecture delves into Configuration Interaction (CI) methods, focusing on the full CI approach for many-electron wavefunctions. It explains the use of Slater determinants to describe electron excitations and the exactness of full CI within a chosen basis set. The lecture also covers the Hartree-Fock ground-state determinant, singly-excited, and doubly-excited determinants. The instructor discusses the matrix equation for the many-electron Schrodinger equation and the Slater rules to determine Hamiltonian matrix elements. Furthermore, the lecture explores the challenges of performing full CI calculations due to the vast number of determinants involved, providing insights into the percentage of correlation energy in various molecules and the application of Many-Body Perturbation Theory to address electron correlation effects.