Nonempirical cluster calculations

Mikheikin et al. (11) have formulated an alternative approach where terminal valencies are saturated by monovalent atoms whose quantum-chemical parameters (the shape of AO, electronegativity, etc.) are specially adjusted for the better reproduction of given characteristics of the electron structure of the solid (the stoichiometry of the charge distribution, the band gap, the valence band structure, some experimental properties of the surface groups, etc.). Such atoms were termed pseudo-atoms and the procedure itself was called the method of a cluster with terminal pseudo-atoms (CTP). The corresponding scheme of quantum-chemical calculations was realized within the frames of CNDO/BW (77), MINDO/3 (13), and CNDO/2 (30) as well as within the scope of the nonempirical approach (16). 

In the present work, we report DFT calculations of hydrocarbons adsorption on Au2o cluster [4]. All calculations were carried out with the nonempirical local PBE (Perdew—Burke—Ernzerhof) functional, which we have used earlier in the study of gold complexes [5]. Calculations were performed with a PRIRODA software [6]. The basis set with the SBK pseudopotential was used [7]. In this pseudopotential, the outer electronic shells are described by the following basis sets H [311/1], C [311/311/11] and Au [51111/51111/5111]. The types of stationary points on potential energy surfaces were determined from analysis of Hessians. The second derivatives were calculated analytically. 

Cl, Br impurities in Ti02 [720,721) without preliminary symmetry analysis of the cyclic clusters chosen. Such an analysis was made in [683] and allowed the convergence of the supercell UHF LCAO calculations of V-doped rutile with the supercell size to be investigated. This first nonempirical superceU LCAO calculation of the defective rutile crystal is discussed here in more detail. 

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