First-principles insights into hydrogen trapping in interstitial-vacancy complexes in vanadium carbide

Area of Science:

• Materials Science
• Physical Chemistry
• Computational Materials Science

Background:

• Hydrogen embrittlement is a critical issue in vanadium alloys and steels.
• The role of carbon vacancies in hydrogen trapping within vanadium carbide remains unclear.

Purpose of the Study:

• To investigate the impact of carbon vacancies on hydrogen trapping in vanadium carbide.
• To elucidate the mechanisms behind enhanced hydrogen trapping due to carbon vacancies.

Main Methods:

• First-principles calculations were employed to model defect complexes in vanadium carbide.
• Electronic structure analysis was used to understand the interactions between hydrogen, carbon vacancies, and vanadium.

Main Results:

• A trigonal interstitial site, adjacent to a carbon vacancy, was identified as a stable hydrogen trapping site.
• Carbon vacancies reduce the solution energy of hydrogen atoms by increasing charge density and Bader atomic volume.
• The V-H bond strength becomes the dominant factor in hydrogen trapping when a carbon vacancy is present.

Conclusions:

• Carbon vacancies significantly enhance hydrogen trapping in vanadium carbide.
• Understanding these effects is vital for developing robust vanadium-based materials resistant to hydrogen embrittlement.
• The findings provide a mechanistic basis for designing advanced vanadium alloys with improved hydrogen management.