Fig. 3.

Desorption barrier of two hydrogen atoms from (A) the metadimer configuration and (B) the paired six adatoms configuration. (C) Migration barrier of two hydrogen adatoms from the paired 24 adatoms configurations into a separated paradimer configuration. IS, TS, and FS stand for initial, transition, and final states, respectively. Blue balls are hydrogen atoms, and the network of carbon atoms is represented by the wireframe. (C, Right) The two carbon atoms from which hydrogen atoms migrated are highlighted with gray balls. Dashed lines are only a guide for the eye. (C, Inset) A zoomed-in view depicting the direction of the migration. Parts of figure adapted from the published data in Ref (75). Copyrighted by the American Physical Society.