Maximum Value of the ABC Index of the Edge‐Corona Graph of Two Graphs

This paper is concerned with the atom‐bond connectivity index (ABC index), defined as , where E ( G ) is the edge set of G and d u and d v are degrees of vertices u and v , respectively. G 1 □ G 2 denotes the edge‐corona graph of G 1 and G 2 . In this paper, we derive the main result: The ABC indices of G 1 □ G 2 attain maximum value if and only if both G 1 and G 2 are complete graphs.