New insight into the interaction between divacancy and H/He impurity in Ti₃AlC₂ using first-principles studies

Area of Science:

• Materials Science
• Computational Materials Science
• Nuclear Materials

Background:

• Ti3AlC2 is a MAX phase material with potential applications in harsh environments.
• Understanding the behavior of light impurities like hydrogen (H) and helium (He) is critical for predicting material performance under irradiation.
• Vacancy defects play a significant role in the microstructure and properties of materials.

Purpose of the Study:

• To investigate the interaction between vacancy defects and H/He impurities in Ti3AlC2 using first-principles calculations.
• To determine the most stable vacancy configurations and their formation energies.
• To analyze the influence of H and He on vacancy formation and the resulting bubble structures.

Main Methods:

• First-principles density functional theory (DFT) calculations.
• Calculation of formation energies for monovacancy and divacancy defects.
• Study of H and He atom configurations within vacancy defects.
• Analysis of H/He-vacancy complex formation energies and structures.

Main Results:

• Aluminum monovacancy (VAl) and Al-based divacancies (2VAl-Al, 2VAl-C) are the most easily formed vacancies.
• Hydrogen atoms preferentially occupy specific interstitial sites within vacancies, with configurations depending on the vacancy type.
• H clusters can promote vacancy formation and lead to platelet-like or spherical bubble structures.
• Divacancies exhibit stronger H trapping than monovacancies, with 2VAl-Al capturing up to seven H atoms.
• Helium impurities reduce H trapping capacity and suppress further H aggregation.

Conclusions:

• The formation and interaction of vacancy defects with H/He impurities in Ti3AlC2 have been elucidated.
• The study provides insights into the microstructural evolution of H/He bubbles in Ti3AlC2 under irradiation.
• These findings are essential for understanding and predicting the behavior of Ti3AlC2 in irradiation environments.