Page | 257 Received: 14 February 2021 Revised: 01 April 2021 Accepted: 07 April 2021 DOI: 10.22034/ecc.2021.277103.1147 Eurasian Chem. Commun. 3 (2021) 257-263 http:/echemcom.com FULL PAPER On the ABC and GA indices of the corona products of some graphs Dhananjaya Kumara |Anuradha Mahasinghe* |Hasitha Erandi Department of Mathematics, University of Colombo, Colombo 03, Sri Lanka *Corresponding Author: A.C. Mahasinghe Tel.: +94778290095 In this research, we derived the formulae for the atom-bond connectivity (ABC) index and the geometric-arithmetic (GA) index of several corona products of graphs made by composing the path, the cycle and the complete graphs. Relevant mathematical results were presented with proofs, indicating the possibility of predicting physicochemical properties of several molecular graphs. KEYWORDS Operations on graphs; corona product; ABC index; GA index; molecular graphs. Introduction A molecular graph is a simple finite and connected graph of which the vertices represent the atoms and the edges represent the bonds between them. Graph invariants defined on molecular graphs, based on the degrees of vertices or the weights of the vertices or the edges are called topological indices. As an extensively studied area in chemical graph theory, these invariants generally help to predict certain physicochemical properties of molecular structures such as boiling point and stability in terms of molecular shapes. Wiener index, the pioneering topological index first appeared in literature in 1947 [10]. Since then, several topological indices including the Wiener index, the Randić index, the atom-bond connectivity (ABC) index, the Gutman index and the geometric-arithmetic (GA) index were studied by several researchers for extracting information of molecular structures mathematically [2,3,8,9]. On the other hand, composition of new compounds from the existing ones can be modeled by graph operations, where a new molecular graph is obtained by combining two molecular graphs. There are several graph operations such as the Cartesian product, the cluster product, the corona product and the Kronecker product, different compositions representing different chemical operations [4,5]. Therefore, it is useful to know the topological indices of these composite molecular graphs, in order to derive important information on their properties [1]. Accordingly, topological indices of product graphs have been an interesting research topic in the past few years and one may find many papers presenting formulae for different topological indices of different compositions of graphs [6,7,9,10]. This is the context based on which we were motivated to study the ABC index [2] and the GA index [9] of the corona products of several graph structures. Preliminaries The ABC index was proposed by Estrada et al in 1998 [2]. The index is based on the