A new geometric–arithmetic index

摘要

A new molecular-structure descriptor GA ₂, belonging to the class of geometric–arithmetic indices, is considered. It is closely related to the Szeged and vertex PI indices. The main properties of GA ₂ are established, including lower and upper bounds. The trees with minimum and maximum GA ₂ are characterized. Keywords Geometric–arithmetic index - Szeged index - PI index - Distance (in graph) - Molecular-structure descriptor