Note on PI and Szeged indices
In theoretical chemistry, molecular structure descriptors are used for modeling physicochemical, pharmacologic, toxicologic, biological and other properties of chemical compounds. In this paper we study distance-based graph invariants and present some improved and corrected sharp inequalities for PI, vertex PI, Szeged and edge Szeged topological indices, involving the number of vertices and edges, the diameter, the number of triangles and the Zagreb indices. In addition, we give a complete characterization of the extremal graphs. (C) 2010 Elsevier Ltd. All rights reserved.
molecular descriptors pi index szeged index zagreb index distance in graphs