Minimum Tracking Linear Response Hubbard and Hund Corrected Density Functional Theory in CP2K.

Area of Science:

• Computational Materials Science
• Quantum Chemistry
• Condensed Matter Physics

Background:

• Density Functional Theory (DFT) often requires corrections for accurate electronic structure calculations of strongly correlated materials.
• Hubbard (U) and Hund (J) corrections (DFT + U + J) are crucial for improving the description of localized electrons.

Purpose of the Study:

• To implement and validate the DFT + U + J functionality within the CP2K software suite.
• To introduce a first-principles method for calculating U and J parameters.
• To benchmark the new implementation against established results for various material properties.

Main Methods:

• Implementation of tensorial and Löwdin subspace representations for DFT + U + J.
• Development of analytical DFT + U + J forces.
• Integration of a minimum-tracking linear-response method for U and J parameter calculation.
• Benchmarking using NiO, TiO2, and hexahydrated transition metals.

Main Results:

• Successful implementation and validation of DFT + U + J functionality in Quickstep (CP2K).
• Accurate prediction of band gaps in NiO and TiO2, including the effect of J corrections.
• Consistent results with literature values for material properties.
• Analysis of the influence of Löwdin orthonormalization on calculated properties.

Conclusions:

• The implemented DFT + U + J method provides a robust tool for accurate materials simulations.
• The first-principles calculation of U and J parameters enhances predictive power.
• The study confirms the importance of U and J corrections for correlated materials.