from first principles PP-I-1

OY-I-1The Theoretical Prediction of Structural and Electronic Effectsof Gold-Based Systems in Selective Alkynes ActivationRatmanova N.K. 1 , Mukhamedzyanova D.F. 1 , Pichugina D.A. 1,2 , Kuz’menko N.E. 11 M.V. Lomonosov Moscow State University, Moscow, Russia2 Institute of Problems of Chemical Physics RAS, Chernogolovka, Russian.ratmanova@gmail.comGold nanoparticles supported on metal oxides are active in the conversion of unsaturatedhydrocarbons. The activation of C=C and С≡С bonds is a key step in hydrogenation,oxidation and isomerization reactions. The investigation of catalytic sites of goldnanoparticles and the evaluation of support influence on these sites is necessary for the designof new highly efficient catalysts.In the present work, the results of simulation of the simplest unsaturated hydrocarbons C 2 H 2and C 2 H 4 adsorption onto neutral and charged cluster Au 12 (2D and 3D isomers), as well asonto the MgO(100) surface are described. The calculations were performed using the densityfunctional theory (DFT/PBE) in the programs “Priroda 08” and “CASTEP 5.5”. Relativisticeffects were taken into account using a scalar-relativistic approach. MgO(100) wasinvestigated using a plane wave basis set and ultrasoft pseudopotentials in periodic boundaryconditions.The adsorption of hydrocarbons (C x H y ) onto Au 12 cluster is accompanied by the formation ofcomplexes, where C x H y bonded with low-coordinated atoms of the cluster. The increase ofthe multiple bond lengths in complexes versus free C x H y is an evidence of hydrocarbonactivation. Molecular orbital analysis of the complexes indicates the interaction to occur via adonor-acceptor mechanism involving the HOMO of the hydrocarbons and the LUMO of thegold cluster. The preferable adsorption of С 2 Н 2 over C 2 H 4 on 3D cluster was found out basedon the calculated adsorption heats. The adsorption of hydrocarbons onto Au + 12 cluster isaccompanied by an increase in adsorption heats for both C 2 H 2 and C 2 H 4 due to effectiveoverlap between frontier orbitals of hydrocarbon and a cluster. The Au - 12 cluster exhibit apronounced selectivity for С 2 Н 2 over C 2 H 4 . It was shown that charge effect is more apparentthan structural effect. Both C 2 H 2 and C 2 H 4 are adsorbed physically on the MgO(100) surface.This work was funded by grant of the President of the Russian Federation for state support ofyoung Russian Ph.D. scientists (МК-107.2011.3) and RFBR (10-03-00999). The calculationswere performed using supercomputer SKIF MSU “Chebyshev”.87