Bijan Taeri - Associate Professor of Mathematics Department of Mathematical Sciences, Isfahan University of Technology, Isfahan, Iran
Mehdi Eliasi - ph.D Candidate of Mathamtics Department of Mathematical Sciences, Isfahan University of Technology, Isfahan, Iran

Topological indices of nanotubes are numerical descriptors that are derived from graph of chemical compounds. Such indices based on the distances in graph are widely used for establishing relationships between the structure of nanotubes and their physico-chemical properties. The Szeged index is obtained as a bond additive quantity where bond contributions are given as the product of the number of atoms closer to each of the two end points of each bond. The Balaban index of a molecular graph calculates the average distance sum connectivity index. Balaban index measures the ramification and it tends to increase with molecular ramification. 1n'this paper we derive the exact expressions for Szeged and Balaban indices of zigzag polyhex nanotubes. Also we compute the Balaban index of zigzag polyhex nanotorus.

Topological indices-Szeged index-Balaban index-Nanotu bes- Nanotorus