The Atom-bond-connectivity index ABC of a graph G is determined by d_i and d_j. In this paper, sharp results for the general which has chemical applications are found using different methods. These new inex investigated in terms its edges, vertices degrees. particular, some relations obtained involving topological indices; Randic index, Zagreb Harmonic Narumi-Katayama index. Indeed, improved he...

A connected graph G is said to be k-connected if it has more than k vertices and remains whenever fewer are deleted. In this paper, for a with sufficiently large order, we present tight sufficient condition fixed minimum degree based on the Q-index. Our result can viewed as spectral counterpart of corresponding Dirac-type condition.

The Harary index of a graph is defined as the sum of reciprocals of distances between all pairs of vertices of the graph. In this paperweprovide anupper boundof theHarary index in terms of the vertex or edge connectivity of a graph. We characterize the unique graph with themaximumHarary index among all graphs with a given number of cut vertices or vertex connectivity or edge connectivity. In ad...

We present an application of the chemical graph theory approach for generating elementary reactions of complex systems. Molecular species are naturally represented by graphs, which are identified by their vertices and edges where vertices are atom types and edges are bonds. The mechanism is generated using a set of reaction patterns (sub-graphs). These subgraphs are the internal representations...

In this paper, we prove that the connectivity and the edge connectivity of the lexicographic product of two graphs G1 and G2 are equal to κ1v2 and min{λ1v 2 2 , δ2 +δ1v2}, respectively, where δi, κi, λi and vi denote the minimum degree, the connectivity, the edge-connectivity and the number of vertices of Gi, respectively. We also obtain that the edge-connectivity of the direct product of K2 an...