A detailed location analysis of metal cations Ni2+, Cu2+, Cr2+, Cd2+ and Pb2+, in six-ring model clusters of zeolite Y structure is reported at the DIPT B3LYP/Lanl2dz level of theory. It has been shown that Cu2+ ion gives the most (-2721.186 kJ/mol) while Pb2+ ion gives the least (-2191.246 kJ/mol) stable binding energies with the stable cluster complexes. The effect of the metal cations on the binding energies has been found in the order Pb2+ < Cd2+ < Cr2+ < Ni2+ < Cu2+ for both types of cluster structures. The location results have shown that the M2+ cations present a four-fold coordination in the zeolite Y structure and M-O bond distances vary between 1.90 and 2.36 angstrom. The HOMO-LUMO energies and NBO analysis of the interacting orbital confirm that p orbital of the zeolite's oxygens behave as donors while d orbital of the Ni2+, Cu2+ and Cr2+ ions and s, p orbital of the Cd2+ and Pb2+ ions behave as a acceptors. (c) 2005 Elsevier B.V. All rights reserved.