One variant on this approach using the exponential of an operator equal to the sum of all n-excitations is called the cluster operator, while another variant useful for nearly-degenerate states models partial occupancy with a complete active space.  
One variant on this approach using the exponential of an operator equal to the sum of all n-excitations is called the cluster operator, while another variant useful for nearly-degenerate states models partial occupancy with a complete active space.  The use of one alternative to this approach is based on the Thomas Fermi model and the HK theorems, and that alternative reduces a problem in three N spacial coordinates to just three.  This method incorporates exchange symmetry with an antisymmetric tensor, which is solved for by the Rooathan equations and built from a linear combination of atomic orbitals. This method also notably features Slater determinants. FTP, name this self consistent field theory, often contrasted with density functional theories, used to calculate electronic wavefunctions of molecules.
One variant on this approach using the exponential of an operator equal to the sum of all n-excitations is called the cluster operator, while another variant useful for nearly-degenerate states models partial occupancy with a complete active space.  
Hartree-Fock Method [accept Post-Hartree-Fock Methods, prompt on "Self Consistent Field theory" before mention, prompt on "Coupled cluster" before "cluster"]