Examples of the reaction rates obtained at different temperatures for different reactions. In (a), (b), (c), reaction rates are considered to increase with temperature and to follow an Arrhenius model. In (d), (e), (f), reaction rates are considered to be constant with temperature and to follow a zero-barrier model. (d) is an example of the creation of a bond between two undercoordinated atoms. (e) is an example of the breakage of a bond between one overcoordinated H and one other atom. (f) is an example of the breakage of a bond between one overcoordinated C with one C bonded to it and one other atom. (c) is an example of the breakage of a bond between one overcoordinated C with two C bonded to it and one other atom, and the behavior is best described by an Arrhenius model compared with (f) where the overcoordinated C is bonded to one C and the behavior with temperature is best described with a zero-barrier model.