Theoretical study of small clusters Au_{3-4} on Au/SAPO-11 catalysts and their interactions with CO

Quantum chemistry calculations were done, using the ONIOM2 methodology at two different levels of calculation, B3LYP for the high level and UFF for the low level. These calculations were performed on Au3/SAPO-11, Au4/SAPO-11, CO-Au3/SAPO-11 and CO-Au4/SAPO-11 aggregates to analyze the geometries of small clusters of Au3 and Au4 on SAPO-11 support. Au3 cluster present a triangle structure in Au3/SAPO-11. Au4 cluster shows a “Y shaped” structure in Au4/SAPO-11. Au4 as a rhombus structure is also studied but it is an unstable intermediate to the “Y shaped” structure. The CO interaction with Au3 and Au4/SAPO-11 is studied, this CO adsorption is different from reported in the literature. The formation energy ΔEF of the aggregates and the CO adsorption energy ΔEads on them are presented.