Development of a Multicenter Density Functional Tight Binding Model for Plutonium Surface Hydriding.

Area of Science:

• Computational materials science
• Surface chemistry
• Quantum mechanics

Background:

• Accurate modeling of hydrogen interactions with plutonium surfaces is crucial for understanding material behavior and reactivity.
• Traditional methods like Density Functional Theory (DFT) can be computationally expensive for large-scale simulations.

Purpose of the Study:

• To develop an efficient and accurate multicenter model for simulating hydrogen on delta-plutonium.
• To validate the model against established computational techniques and experimental relevance.
• To investigate the energetics of hydrogen dissociation and diffusion on plutonium surfaces.

Main Methods:

• Development of a Density Functional Tight Binding (DFTB) model incorporating new Slater-Koster parameters.
• Utilized the Chebyshev Interaction Model for Efficient Simulation (ChIMES) for repulsive energy calculations.
• Performed molecular dynamics and minimum energy pathway calculations on δ-Pu (100) and (111) surfaces.

Main Results:

• The DFTB/ChIMES model accurately reproduces the electron density of states for bulk δ-Pu compared to DFT.
• Calculations show good agreement with approximate H2 dissociation paths on the δ-Pu (100) surface.
• Determined the energetics for surface dissociation and subsurface diffusion of hydrogen on δ-Pu surfaces.

Conclusions:

• The developed DFTB/ChIMES model offers an efficient approach for multicenter repulsive energy calculations.
• This method requires a reduced computational cost compared to traditional DFT, facilitating complex simulations.
• The model is valuable for interpreting and validating quantum calculations in experimental studies of plutonium reactivity.