First-principles molecular dynamics of H₂ molecule formation inside hydrogenated amorphous carbon

A carbon layer redeposited by plasma on a plasma facing wall is an important element for understanding tritium recycling in fusion power generation. The characteristics of this redeposited layer need to be thoroughly investigated, and hydrogenated amorphous carbon is considered a potential model for this purpose. In this study, first-principles molecular dynamics simulations were conducted to investigate the initial formation behavior of H₂ molecules inside amorphous carbon, and systematic data on the relationship between the number of C-H bonds and H₂ molecule formation were provided. The results suggest that the saturation of C-H bonds is the important factor in H₂ molecule formation. This structural model is expected to contribute to further simulation studies on the characteristics of redeposited layers concerning tritium cycling.