Natural determinant reference functional theory.

Area of Science:

• Quantum Chemistry
• Computational Physics
• Materials Science

Background:

• The natural determinant reference (NDR) is the Slater determinant of the most occupied natural orbitals for an N-electron system.
• Unlike Kohn-Sham (KS) determinants, NDR provides an idempotent approximation to the interacting one-particle reduced density matrix.
• NDR is well-defined in standard basis sets and is invariant to representation.

Purpose of the Study:

• To overcome the under-determination problem in defining ground-state energy functionals for NDR.
• To develop a variational method for determining ground-state energy, NDR, ionization potentials, and electron affinities.
• To establish Natural Determinant Reference functional theory as an exactification of orbital optimization and generalized KS methods.

Main Methods:

• Utilizing a grand-canonical ensemble framework at the zero-temperature limit.
• Developing a grand potential functional based on the NDR ensemble.
• Formulating NDR functionals dependent on the noninteracting Hamiltonian.

Main Results:

• The grand potential functional enables variational determination of ground-state energy and its corresponding NDR (ensemble).
• The method accurately predicts select ionization potentials and electron affinities.
• NDR functional theory provides an alternative to KS-inversion and optimized effective potentials.

Conclusions:

• The grand-canonical ensemble approach successfully addresses prior limitations in NDR functional theory.
• NDR functional theory offers a robust and accurate method for electronic structure calculations.
• This approach simplifies calculations by avoiding KS-inversion and optimized effective potentials.