On the other hand, theoretical studies have been limited so far regarding the Pd zeolite heterogeneous catalysts. The first DFT calculations of the Pd4 cluster in zeolite were carried out by Jerzy Moc et al.14 The Pd4 cluster supported over siliceous FAU zeolite was used to study the dissociation of the H2 molecule. In this system, the Pd4 cluster in the tetrahedral (Td) structure was shown to be stable in the triplet state. The H2 activation on the Pd4 cluster over the H-FAU zeolite was also investigated using the ONIOM (Our own N-layered Integrated molecular Orbital and molecular Mechanics) method.