Features of Helium-Vacancy Complex Formation at the Zr/Nb Interface

Area of Science:

• Materials Science
• Computational Materials Science
• Surface Science

Background:

• Understanding interfaces is crucial for material performance.
• Helium impurities can degrade material properties.
• Atomic interactions at interfaces influence defect behavior.

Purpose of the Study:

• Investigate atomic structure and electron density at the Zr/Nb interface.
• Determine the impact of helium impurities and helium-vacancy complexes.
• Analyze defect formation energies and preferred locations.

Main Methods:

• First-principles study.
• Optimised Vanderbilt pseudopotential method.
• Calculation of formation energy for Zr-Nb-He system.

Main Results:

• Helium atoms and complexes preferentially form in the first two Zr layers at the interface.
• This increases reduced electron density areas in the first Zr layers.
• Helium-vacancy complexes reduce electron density defects in deeper Zr/Nb layers and bulk.
• Vacancies in the first Nb layer attract Zr atoms, potentially self-healing defects.

Conclusions:

• Helium impurity localization at the Zr/Nb interface is confirmed.
• The interaction between helium, vacancies, and the interface alters electron density distribution.
• Potential self-healing mechanisms for Nb-side vacancies were identified.