DFT + U Study of Uranium Dioxide and Plutonium Dioxide with Occupation Matrix Control

Area of Science:

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

Background:

• Accurate theoretical modeling of actinide oxides like UO2 and PuO2 is essential for nuclear energy and waste management.
• Previous studies have faced challenges in precisely predicting the electronic and magnetic properties of these materials.

Purpose of the Study:

• To computationally investigate bulk UO2 and PuO2 using Density Functional Theory (DFT) with occupation matrix control (OMC).
• To determine optimal DFT+U parameters for accurate prediction of material properties.
• To study PuO2 for the first time using this methodology.

Main Methods:

• Application of DFT+U with occupation matrix control (OMC).
• Utilized the PBESol functional for calculations.
• Simulated lattice parameters, magnetic moments, band gaps, and densities of states.

Main Results:

• Identified antiferromagnetic (AFM) and non-magnetic (NM) ground states for UO2 and PuO2, respectively, aligning with experimental data.
• Recommended U = 4.0 eV for AFM UO2, showing good agreement with experimental properties.
• Suggested U = 4.5 eV for NM PuO2 and U = 4.0 eV for AFM PuO2, noting higher U values are needed for the recently reported PuO2 band gap.

Conclusions:

• DFT+OMC provides a reliable method for studying actinide dioxides.
• The recommended U values offer accurate predictions for UO2 and PuO2 properties.
• The presence of similar excited states highlights the importance of employing OMC for accurate ground-state determination.