Spectral-partitioned Kohn-Sham density functional theory.

Area of Science:

• Computational Physics
• Quantum Chemistry
• Materials Science

Background:

• Kohn-Sham density functional theory (DFT) is a cornerstone for electronic structure calculations.
• Approximating the Kohn-Sham free-energy functional remains a computational challenge, particularly for complex systems.
• Existing methods may struggle with systems exhibiting diverse electronic behaviors across energy scales.

Purpose of the Study:

• To introduce a general, variational scheme for approximating Kohn-Sham free-energy functionals.
• To develop a method that systematically partitions the density matrix into spectral domains.
• To enable more efficient and accurate calculations for systems like warm-dense matter.

Main Methods:

• A variational scheme is proposed, partitioning the density matrix into independent spectral domains.
• Generalized entropic contributions to free energy are used, allowing independent representations.
• A numerical procedure is devised for calculating generalized entropy associated with spectral partitioning.

Main Results:

• The proposed scheme provides an upper bound to the exact Kohn-Sham free energy.
• Applied to warm- and hot-dense matter, it significantly reduces computational cost at high temperatures.
• The method addresses limitations in standard projector-augmented wave (PAW) method completeness at high temperatures.

Conclusions:

• Spectral partitioning offers a powerful framework for Kohn-Sham calculations of systems with multi-energy regime occupied subspaces.
• The method demonstrates substantial computational savings for warm-dense matter simulations.
• This approach provides a systematic solution for challenges in electronic structure calculations at high temperatures.