Computation of the Forgotten Topological Index and Co-Index for Carbon Base Nanomaterial

Molecular topological indices are numerical descriptor of molecular structure obtained via molecular graph G. The forgotten topological index F(G) is a vertex degree based topological index and it can be expressed with F(G)=∑d(v)3=∑d(u)2+d(v)2, where d(u) denotes the degree of u. The forgotten co-index Co-F(G) is defined as the sum of squares of a graph’s vertex degrees which is not adjacent. In this study, the F(G) and Co-F(G) index of HAC5C7, HAC5C6C7, linear [n]-phenylenes and cyclic phenylenes nanostructures are computed for possible works in the properties of molecules such as structure–property relationship. In addition, polynomials of the forgotten index and co-index are found for these nanostructures.