M. S. Shapnik

Water adsorption—quantum chemical approach

The chemisorption of a single water molecule on the Cu, Ag, Au and Zn, Cd, Hg low index faces and of the (H2O)n associates (n = 2−5) on Ag(111) and on a close-packed mercury surface has been investigated by CNDO method together with geometrical optimization of the atom positions. For substrate, a cluster consisting of a few atoms, as a model, has been used. A new “microscopic” sequence of the metal hydrophilicity is proposed. Calculations are critically discussed in the light of experimental and other quantum chemical data. Water structuring near a mercury surface has been also studied by using Metropolis Monte Carlo procedure.

Quantum-chemical investigation of the formation of Lewis acid centers of high-siliceous zeolites

AM1 quantum-chemical model calcualtions of the dealumination process in high-siliceous zeolites have confirmed the thermodynamical possibility of Lewis center formation mechanism previously suggested by other authors. The structure and local charge distribution for the Lewis centers of two arts produced at this process were studied in detail. The calculated values of the NH3 and CO adsorption energies on these L-centers allowed for conclusion about their relative acidity.

Molecular–Continuum Model for the Cyanide Ion Adsorption from Aqueous Solutions on Copper Metals

Quantum-chemical calculations of the cyanide ion adsorption from aqueous solutions on copper metals are performed for the first time in a combined molecular–continuum model of polar solvent. The calculations use the cluster model of the surface and are carried out by the density functional in the B3LYP version. The effect of the adsorption systems polar dielectric environment is considered in a self-consistent reactive field model, namely, the SCIPCM model. The dielectric cavity is built in SCIPCM self-consistently with the particles electron density distribution in solution. Calculations show that the CN– adsorption energy decreases in the sequence Au > Cu > Ag. The calculated energy agrees best with the experimental data when the molecular–continuum model is used, rather than the simpler molecular and continuum models.

Quantum-chemical Calculation of Standard Redox Potentials of Half-reactions Involving Bismuth Aquacomplexes

The most probable coordination numbers for aquacomplexes of Bi(III), Bi(II), and Bi(I) ions are found in terms of a density functional method (version B3LYP) with allowance for the effect of dielectric medium in the self-consistent reaction field model. Thermodynamic parameters of hydration of these ions are calculated and used for evaluating standard redox potentials of half-reactions involving the ions.

Quantum-Chemical Study of Electroreduction Mechanism of Copper(I) Cyanide Complexes

Mechanism of electroreduction of copper(I) cyanide complexes from aqueous electrolytic solutions is studied within a quantum-chemical method of a density functional and a quantum-mechanical theory of charge transfer in polar environment. The electrochemically active form directly participating in an elementary electroreduction act is shown to be the [Cu(CN)2]– complex. Modeling calculations of the activation energy for an elementary charge transfer act reveal for the first time that the transfer of heavy particles along an adiabatic potential energy curve is a more probable mechanism of electroreduction of copper(I) cyanocomplexes than an outer-sphere electron transfer.

Electrodeposition of bismuth from a trilon B-sulfosalicylate bath

Bismuth electrodeposition from baths containing bismuth nitrate, trilon B (disodium ethylenediaminetetraacetate Na2H2Edta), and sulfosalicylic acid H3SSA was studied with various ratios of the bath components. Adding H3SSA to the bath made the deposit become semibright and its current efficiency enhance.

Effect of the Ligand Nature in Zinc(II) Complexes on the Inner-Sphere Reorganization in the Electron Transfer Reactions

The effect of the ligand surrounding on the character and degree of the inner-sphere reorganization during electroreduction of aqua, aquahydroxy, hydroxy, and Edta complexes of zinc(II) is studied in the framework of a quantum-chemical approach. It is established that the most substantial intramolecular reorganization occurs during the transfer of the first electron onto [Zn(Edta)]2–. The solvents reorganization energy is estimated.

Electroreduction of Zn(II) Hydroxy-complexes in Aqueous Electrolytes: A Quantum-chemical Study

The quantum-mechanical theory of the charge transfer in polar media is used to demonstrate that, despite the predominance of high-coordinated Zn(II) hydroxy-complexes in electrolyte, their discharge is preceded by a ligand abstraction stage with the formation of neutral species [Zn(OH)2], which theoretically substantiates experimental facts.

Structure of complexes forming over a wide pH range in the Zn(II)-En-H2O system

Quantum-chemical calculations of various forms and isomers of ethylenediamine (En) and structures of ethylenediamine zinc(II) complexes existing over a wide pH range (0–14) have been performed using the density functional theory in the PBE version. The structural, energetic, and charge characteristics of the stable forms of complexes are presented.

Interaction of Chloride Anion and Chlorine Atom with Indium and Gallium Surfaces: A Quantum-chemical Study

The adsorption of the chloride ion and chlorine atom on clusters simulating the surface of the (111) and (001) faces of the crystal lattice of indium and liquid gallium are calculated using the Hartree–Fock–Roothaan and density functional (B3LYP) quantum-chemical methods. The energy of adsorption of chloride ions from a gas phase at these faces increases in the following series: bridge≈hollow < on-top positions and equals to ∼179 kJ mol–1 for In(111) and ∼183 kJ mol–1 for gallium in the on-top position. Both metals exhibit similarity in the formation of bonds between their surface atoms and the adsorbate. The adsorbate charge does not depend on the adsorbed form (chloride ion or chlorine atom) and equals ∼ 0.5e. Parameter of a virial adsorption isotherm is estimated with allowance for coulombic interactions near the metal/electrolyte interface.