A detailed location analysis of metal cations Ni2C, Cu2C, Cr2C, Cd2C and Pb2C, in six-ring model clusters of zeolite Y structure is
reported at the DFT B3LYP/Lanl2dz level of theory. It has been shown that Cu2C ion gives the most (K2721.186 kJ/mol) while Pb2C ion
gives the least (K2191.246 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 Pb2C!Cd2C!Cr2C!Ni2C!Cu2C for both types of cluster structures. The location results have
shown that the M2C cations present a four-fold coordination in the zeolite Y structure and M–O bond distances vary between 1.90 and
2.36 A ° . 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 Ni2C, Cu2C and Cr2C ions and s, p orbital of the Cd2C and Pb2C ions behave as a acceptors.