Optimized structure of U adsorbed on the bridge site of graphene in side view. The brown atoms denote the carbon atoms in the supercell, the blue atom represents the U atom, and the green atoms refers to the nearest carbon atoms to the U atom. Symbol ‘h’ in the dot line denotes the adsorption height of the U atom; symbol ‘d’ in the solid line represents the distance between the U atom and the nearest C atom; and symbol ‘Δh’ between the two arrows refers to the graphene distortion.