III International Conference

PP-I-67CALCULATIONS OF CO ADSORPTION ENERGY ON TRANSITION METALCARBIDES AND OXIDES BY IBM AND UBI-QEP METHODSКuz’min А.Е.Topchiev Institute of Petrochemical Synthesis RAS, Moscow, RussiaE-mail: kuzmin@ips.ac.ruResults of estimation of CO adsorption energy on the surfaces of some transition metaloxides and carbides by empirical methods of interacting bonds (IBM) and UBI-QEP arepresented. The results are compared with experimental values of adsorption energy andresults of ab initio calculations; it is shown that IBM allows to obtain better qualitative andquantitative agreement between estimated and experimental values rather than UBI-QEP, andso it is a promising method for vast calculations of properties of reaction intermediates on realcatalytic surfaces.The development of the approach to realization vast calculations of characteristics ofintermediate species and elementary reactions in catalysis and, accordingly, to a prediction ofcatalytic action approved earlier [1] with the use of variational empirical methods –interacting bonds method (IBM) [2] and UBI-QEP [3] – is presented. IBM advantage overwide-known UBI-QEP has been shown on the examples of CO and СН 3 adsorption energycalculations for ideal and defected surfaces of some transition metals [1]. IBM not only hasshown better agreement between estimated adsorption energies and experimental and ab initiovalues than UBI-QEP, but also appeared to be able to describe correctly changes ofadsorbtion energies on some defects (step, kink), that is impossible in principle for UBI-QEP.Moreover, IBM basic equation determining atomisation energy Н ат of a speciesН ат =Σγ i (2-γ i )E i -ΣΣγ i γ j Δ ij (γ i is varied independently)i> jas against apparently similar UBI-QEP equationН ат =Σγ i (2-γ i )E i (for the selected bonds Σγ i =1)has a quantum mechanical validation [2].Just as the presentation [1] have targeted a model transition from ideal metal catalysts torealistic ones so the next logical step is an application of IBM and UBI-QEP for calculationsof adsorption energies on chemically nonuniform catalytic surfaces; here CO adsorption onthe surfaces of VIII group metal oxides and carbides is considered. The obtained results showthat UBI-QEP (as against a situation with defective surfaces) is able in principle to take into127