Bounds for the augmented Zagreb index

Abstract

The augmented Zagreb index (\rm{AZI} for short) of a graph $G$, introduced by Furtula et al. in 2010, is defined as ${\rm AZI}(G)=\sum\limits_{v_iv_j\in E(G)}{\left(\frac{d(v_i)d(v_j)}{d(v_i)+d(v_j)-2}\right)}^3$, where $E(G)$ is the edge set of $G$, and $d(v_i)$ denotes the degree of the vertex $v_i$. In this paper, we give some new bounds on general connected graphs, molecular trees and triangle-free graphs. \\[2mm] {\bf Keywords:} Agumented Zagreb index; molecular trees; Triangle-free graph