ИСТИНА

Scalar-relativistic DFT with modified Dirac-Coloumb-Breit Hamiltonian and the nonempirical local PBE functional are applied. To check the accuracy of theoretical approach, the characteristics of small Au-, Pd- and Ni-containing molecules (Re, vibrational frequencies, I, A, De) have been calculated. Calculated values are close enough to experimental data and well agree with results obtained all-electron methods.<br> Mixed AuPd and AuNi clusters are optimized for the various accessible spin multiplicities (SM). For pure gold clusters only singlet and doublet SM for even or odd number of electrons are considered. It is obtained that in AunNi clusters the average interatomic distances increase. The maximum value of Me-Me bond length changing is 0,024 A for Au4Ni cluster. The calculated bond energies per atom increase when the numbers of atoms in clusters increase. It has been shown, that in AuPd bclusters the charge in Pd atom oscillates depending on composition of a cluster, while most gold atoms are negativily charged. Some discrepancies are between Mulliken and NPA schemes of calculation, and Hirshfeld, where Pd possesses different charge. In order to clarify the nature of M-Au binding in clusters the visualization of HOMO is carried out. Highest occupied molecular orbilas up to HOMO-2 in Au6Pd are formed through the overlap of Au and Pd d-orbitals, representing the bonds between these atoms in the cluster. At the same time the HOMO in Au6Ni reflect the position of three different lone pairs on the Ni atom, while the bonding orbitals have lower energy, indicating the higher stability of this cluster. This fact is confirmed by calculation of binding energies and reflects the tendency which is common for all bimitallic AunX clusters.<br> Au4Pd4 cluster demonstrates higher catalytic activity in the direct synthesis of hydrogen peroxide than the Au8 cluster, because in the case of Au4Pd4 energy barrier of hydrogen atom migration to the ООН∙, leading to the formation of H2O2, is about two times lower than in the formation of H2O2 on the cluster Au8. The study of allylbenzene isomerization in the presence of Au4 and Au3Ni reveal that transition state in the (allylbenzene-Au3Ni) system corresponds to lower activation energy in comparison to the system with Au4.