The zero-barrier model was employed for four different types of reactions: the creation of a bond between two undercoordinated atoms, the breaking of a bond between two overcoordinated atoms, the breaking of a bond between one overcoordinated hydrogen and any other atom, and the breaking of a bond between one overcoordinated carbon with one or zero carbon bonded to it and any other atom. The justification for this choice is as follows. The two undercoordinated atoms case is commonly considered as having a zero-barrier energy as the two atoms will both be more stable if they followed the octet (for carbons) or duet (for hydrogen) rule. The two overcoordinated atoms cases are not usually considered in traditional kinetic models; therefore, there is no common treatment for them. We have chosen to employ the zero-barrier model in this case because the two overcoordinated atoms would be more stable if their bond was broken, i.e., a similar reason justifying zero-barrier model for undercoordinated atoms. However, breaking a bond between one overcoordinated atom and one stable atom induces the creation of one stable atom and one undercoordinated atom. For these cases, the decision of which model to employ was based on the trends observed in the training data. Some examples are shown in Fig. . All other reactions were assumed to follow the Arrhenius model, particularly any reaction involving three atoms was assumed to follow Arrhenius model.