Topological indices are employed to figure out the physicochemical properties and bio-activity of chemical compounds in QSAR/QSPR. Quantitative Structure-Property Relationship (QSPR) and Quantitative Structure-Activity Relationship (QSAR) studies are indisputably have greater significance in biochemistry, modern chemistry as well as in drug designing. Among the topological indices geometric-arithmetic index is a family of indices shows a high correlation with several physicochemical properties of alkanes. Inspired by splendorous utilization of geometric-arithmetic index, we propose here a new sixth geometric-arithmetic index  to the family of geometric-arithmetic index. The sixth geometric-arithmetic index  shows a very good correlation with the acentric factor (AcenFac) of octane isomers. Moreover, in this paper we compute  of line graphs of subdivision graphs of 2D-lattice, nanotube and nanotorus of 

molecular descriptor, geometric-arithmetic index, sixth geometric-arithmetic index, nanostructures.