Density functional insights of iodine interaction with graphene and its nanoribbon with zigzag edges

Graphene, being perfect 2-D structure, exhibits electronic properties which are sensitive to the presence of any impurtiy/adsorbed adatom. In the present work, interaction of I atoms has been investigated with graphene and zigzag graphene nanoribbon (ZGNR) by considering it, as a passivating element as well as an adsorbed adatom. Three different possible combinations of I passivation have been explored which include: one edge I and other edge H passivation (H-ZGNR-I), both edges passivation I (I-ZGNR-I) and one edge I passivation while other edge is passivated by H in sp(3) manner (H-2-ZGNR-I). Similarly, three adsorption sites namely top (T), bridge (B) and hole (H) have been considered at ZGNR as well as on planar graphene sheet. It is revealed that passivation of I on ZGNR is energetically favorable and settled in antiferromagnetic (AFM) ground state. Further, it is observed that H-ZGNR-I is the most stable configuration after pristine (H-ZGNR-H) followed by H-2-ZGNR-I and I-ZGNR-I configurations. Our observations show that except I-ZGNR-I, all the structures exhibit magnetic stabilization well above the thermal excitations at room temperature which ensures their applicability for practical applications. Moreover, I adsorption always prefers T site on ZGNR/graphene sheet. Analysis of I migration on 2-D graphene indicates that diffusion barrier is always less than the thermal excitation energy (similar to 26 meV) and the diffusion time varies from similar to 1.5 ps to similar to 2.2 ps. Present findings suggest for stronger binding of I atoms with ZGNR whereas the same with graphene is comparatively weak and exhibits spontaneous migration.