Simulated hydrogen diffusion in diamond grain boundaries

• Published in: Diamond and related materials 2024-11, Vol.149, p.111665, Article 111665
• Main Authors: Pittard, J.A., Lavrentiev, M.Y., Fox, N.A.
• Format: Article
• Language: English
• Subjects: Diamond; Diffusion; Grain boundary; Hydrogen; Molecular dynamics
• ISSN: 0925-9635
• DOI: 10.1016/j.diamond.2024.111665

To evaluate hydrogen diffusion within diamond, a series of molecular dynamics simulations have been carried out in which diffusion coefficients and activation energies were determined. Diamond grown via chemical vapour deposition (CVD) contains a high hydrogen concentration within grain boundaries, because of this, common tilt grain boundaries were recreated from transmission electron microscopy images taken from literature. Diffusion coefficients of hydrogen placed within the grain boundary were estimated and compared to the bulk diffusion. Unlike many crystalline structures, some grain boundaries presented limited diffusion when compared to the bulk. Diffusion characteristics of grain boundaries are thought to be a result of channelling effects combined with the formation of sp3C-H bonds with sp2 carbon present within some grain boundaries - increasing and decreasing diffusion rates respectively. Potential wells were observed across some but not all the grain boundaries resulting in hydrogen trapping and anisotropic diffusion. [Display omitted] •Common, physical, diamond grain boundaries reproduced in simulation•Diffusion coefficients calculated for hydrogen in grain boundaries•Channels and different bonding present in grain boundaries restricted diffusion•Hydrogen trapped within most grain boundaries tested