Abstract:

Reference states and systems underlie almost any quantum chemical calculation. Hartree-Fock and Kohn-Sham Density Functional Theory are references well-established as the fundamentals to anyone dabbling in theoretical and computational chemistry. What can be seen as a form of departure from the Kohn-Sham construction, the Natural Determinant Reference (NDR) density matrix best approximates the interacting one-particle reduced density matrix in the Frobenius 2-norm. An NDR Functional Theory forms a promising option of a non-interacting starting point alternative for future calculations. Its formalism and a roadmap to deriving functionals revolving around this quantity are established.