The 2nd REBO potential was developed by Brenner et al. , containing improved analytical functions and an extended database relative to the earlier version . In addition, a long-ranged interaction WEHI-539 considered making the 2nd REBO potential more accurate than its previous version. The detailed information of the 2nd REBO potential is presented below:equation(1)Eb=∑i∑jj>iVRrij−bijVArijequation(2)VRr=fcr1+QrAexp−αrequation(3)VAr=fcr∑n=1,3BnAexp−βnrequation(4)fijcr=11+cosπr−DijminDijmax−Dijmin/20r<DijminDijmin<r<Dijmaxr>Dijmaxwhere Eb represents the chemical binding energy, and VR and VA are pair-additive interactions proteinoids represent all interatomic repulsions and attraction from valence electrons, respectively. rij is the distance between pairs of nearest-neighbor atoms i and j, and bij is a bond order between atoms i and j. fijc(r) is a smoothing cutoff function, having a form shown in Eq. (4). All parameters used in Eqs. (1), (2), (3) and (4) are shown in Table 1.