On the self-consistency of DFT-1/2

Area of Science:

• Computational materials science
• Quantum chemistry
• Solid-state physics

Background:

• Density Functional Theory (DFT) methods like LDA and GGA often struggle with accurate bandgap prediction.
• DFT-1/2 is a bandgap rectification technique, with suggested use of non-self-consistent for ionic insulators and self-consistent for others.
• A lack of clear criteria for choosing between self-consistent and non-self-consistent DFT-1/2 creates ambiguity.

Purpose of the Study:

• To analyze the effect of self-consistency in DFT-1/2 calculations across various insulator types.
• To provide a quantitative understanding of self-consistency's impact on electronic structure and bandgaps.
• To resolve the ambiguity in applying DFT-1/2 to different materials.

Main Methods:

• Investigated self-consistent and non-self-consistent DFT-1/2 and shell DFT-1/2.
• Calculations were performed on insulators and semiconductors with varying ionic and covalent bonding characteristics.
• Analyzed electron localization, self-energy corrections, and bandgap behavior.

Main Results:

• Self-consistency is crucial for accurate electronic structure details in all insulators, even highly ionic ones.
• Self-consistent LDA-1/2 localizes electrons more accurately around anions, rectifying LDA's delocalization error but with potential overcorrection.
• Non-self-consistent LDA-1/2 leads to excessive electron localization and artificially inflated bandgaps, particularly in mixed ionic-covalent compounds.

Conclusions:

• Self-consistent DFT-1/2 is necessary for reliable electronic structure calculations in insulators and semiconductors.
• Non-self-consistent DFT-1/2 introduces significant errors, overestimating localization and bandgaps.
• This study clarifies the application of DFT-1/2, advocating for self-consistent approaches universally.