Computing the PI index of some chemical graphs related to nanostructures

Abstract

The Padmakar-Ivan (PI) index of a graph G is defined as PI(G) = ∑[neu(e|G) + nev(e|G)], where neu(e|G) is the number of edges of G lying closer to u than to v, nev(e|G) is the number of edges of G lying closer to v than to u and summation goes over all edges of G. The PI Index is a Szeged-like topological index developed very recently. In this paper we report on new results about computing PI index of nanotubes. © 2006 IOP Publishing Ltd.