Sohail Zafar2018-10-162018-10-162016Yan, L., Li, Y. F., Farhani M. R., Jamil M. K., Zafar S. (2016). Vertex version of Co-PI index of the polycyclic aromatic hydrocarbon systems PAHk. International Journal of Biology, Pharmacy and Allied Sciences, 5(6), 1244-1253. (Sohail Zafar (Mathematics /SSC), (NOT RECOGNIZED BY HEC))2277–4998https://escholar.umt.edu.pk/handle/123456789/3337Let G be a simple connected graph having vertex set V and edge set E. The length of the smallest V(G) is called the distance, d(u,v), between the vertices u,v.path between vertices u,v Mathematical chemistry is the area of research engaged in new application of mathematics in chemistry. In mathematics chemistry, we have many topological indices for any molecular graph, that they are invariant on the graph automorphism. The length of the smallest path V(G) is called the distance, d(u,v), between the vertices u,v. For an edgebetween vertices u,v E(G), nu(e|G) represents the number of vertices of G whose distance to u is less than thee=uv distance to v in G and nv(e|G) represents the number of vertices of G whose distance to v is less than the distance to u in G. In 2010, A Iranmanesh et.al introduced the new topological indices. The Co-PIv index is the vertex version of Co-PI topological index and is defined as Co PI G n e G n e G  In this present study, we introduce a closed formula of    this new index of the Polycyclic Aromatic Hydrocarbon systems PAHkenMathematicsMolecular graphs, chemical structures Polycyclic Aromatic Hydrocarbon (PAHk), Circumcoronene series of Benzenoid; Padmakar-Ivan index; Co-PI index; Cut Method; Orthogonal Cut.Article