Self-interaction and strong correlation in DFTB

Area of Science:

• Computational Chemistry
• Condensed Matter Physics
• Quantum Chemistry

Background:

• Density Functional Theory (DFT) offers advancements for Density Functional based Tight-Binding (DFTB) methods.
• DFTB provides a platform for testing new DFT extensions.
• Charge-self-consistent DFTB (SCC-DFTB) is a valuable computational tool.

Purpose of the Study:

• To demonstrate the variational nature and ground-state existence in SCC-DFTB.
• To present improved functionals for SCC-DFTB, addressing limitations in describing electronic properties.
• To introduce novel methods for enhancing the accuracy of SCC-DFTB calculations.

Main Methods:

• Demonstration of the variational nature of SCC-DFTB.
• Application of recent LDA+U functionals within the SCC-DFTB framework.
• Development of a semilocal self-interaction correction scheme.
• Introduction of a novel method to address derivative discontinuities.

Main Results:

• Proof of a defined ground-state for SCC-DFTB methods.
• Successful implementation of LDA+U functionals, including a new self-interaction correction.
• Development of a method for exact derivative discontinuities at low computational cost.
• Illustration of these developments using the NiO system.

Conclusions:

• SCC-DFTB possesses a defined ground state, validating its theoretical foundation.
• The presented LDA+U functionals and correction schemes significantly enhance the accuracy of SCC-DFTB.
• Novel methods effectively introduce crucial physical properties like derivative discontinuities, improving electronic structure predictions.