Mohammad Farahani - Department of Mathematics, Iran University of Science and Technology (IUST), Narmak, Tehran ۱۶۸۴۴, Iran

Among topological indices, Zagreb indices are very important, very old and they have many useful properties in chemistry and specially in mathematics chemistry. First and second Zagreb indices have been introduced by Gutman and Trinajstić as M_۱(G)=\sum_{uv\in E}d_u+d_v and M_۱(G)=\sum_{uv\in E}d_ud_v, where du denotes the degree of vertex u in G. Recently, we know new versions of Zagreb indices as M_۱^{*}(G)=\sum_{uv\in E}ecc(u)+ecc(v), M_۱^{**}(G)=\sum_{u\in V}ecc(u)^۲  and M_۲^{*}(G)=\sum_{uv\in E}ecc(u)ecc(v), where ecc(u) is the largest distance between u and any other vertex v of G. In this paper, we focus one of these new topological indices that we call fifth Zagreb index M_۲^*(G)=M_۵(G) and we compute this index for a famous molecular graph Circumcoronene series of benzenoid Hk, k≥ ۱.

First Zagreb index, second Zagreb index, Fifth Zagreb index, Circumcoronene series of benzenoid, Cut Method, Ring-cut Method