Using classical many-body structure to determine electronic structure: An approach using k-electron distribution functions

The quantum N-electron structure problem is expressed as a classical N-body structure problem plus a quantum many-body problem with a reduced number of variables. This forms the foundation of a method for solving the electronic structure problem using k-electron distribution functions instead of many-electron wave functions. The method represents a unified approach to the entire hierarchy of generalized density-functional theories, beginning with standard density-functional theory (k=1) and pair density-functional theory (k=2) and culminating in an exact treatment of the entire N-electron system (k=N).