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Kohn-Sham density functional theory with the available exchange–correlation functionals is less accurate for strongly correlated systems, which require a multiconfigurational description as a zero-order function, than for weakly correlated systems, and available functionals of the spin densities do not accurately predict energies for many strongly correlated systems when one uses multiconfigurational wave functions with spin symmetry. Furthermore, adding a correlation functional to a multiconfigurational reference energy can lead to double counting of electron correlation. Multiconfiguration pair-density functional theory (MC-PDFT) overcomes both obstacles, the second by calculating the quantum mechanical part of the electronic energy entirely by a functional, and the first by using a functional of the total density and the on-top pair density rather than the spin densities. This allows one to calculate the energy of strongly correlated systems efficiently with a pair-density functional and a suitable multiconfigurational reference function. This article reviews MC-PDFT and related background information.
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MuAPBEK: An improved analytical kinetic energy density functional for quantum chemistry
Orbital-free density functional theory (OFDFT) enables full quantum-mechanical simulations based solely on electron densities but is limited by the lack of accurate kinetic-energy functionals. We improve upon the APBEK functional by tuning its μ parameter for a given system during density initialization and adding two non-empirical corrections based on Kato’s cusp condition and the virial theorem. The resulting functional, MuAPBEK, assessed on atoms and molecules, shows significantly lower energy errors than standard APBEK and Thomas–Fermi–von-Weizsäcker functionals, even when evaluated on converged Kohn–Sham density functional theory (KSDFT) densities. MuAPBEK also produces accurate densities that slightly deviate from those of KSDFT. Its density optimization step is over ten times faster than a single KSDFT SCF cycle and scales as O(N1.96), indicating that accurate, large-scale OFDFT simulations are feasible beyond practical KSDFT limits.
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- Award ID(s):
- 2118201
- PAR ID:
- 10644009
- Publisher / Repository:
- American Institute of Physics
- Date Published:
- Journal Name:
- The Journal of Chemical Physics
- Volume:
- 163
- Issue:
- 16
- ISSN:
- 0021-9606
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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