Abstract Among topological descriptors topological indices are very important and they have a prominent role in chemistry. One of them is atom-bond connectivity (ABC) index defined as where dv is the degree of vertex v. Recently, a new version of atom-bond connectivity (ABC4) index was introduced by M. Ghorbani et. al. [38] in 2010 and is defined as where and NG (u) = {vV (G)|uvE(G)}. In this paper we compute this new topological index for Polycyclic Aromatic Hydrocarbons PAHk.
Keywords Topological index, Atom bond connectivity index. Polycyclic Aromatic Hydrocarbons PAHk.