Simulation of the geometric and electronic structures and properties of extrinsic defects involving germanium in lead telluride

Cluster simulation of the bulk and surface of crystalline lead telluride has been performed in the framework of the hybrid density functional theory B3LYP method with the use of the LANL2 pseudopotential with the corresponding double-zeta basis set. Different variants of doping germanium atoms in a PbTe single crystal and at its surface have been examined. Clusters of different sizes have been considered. For the optimal cluster, containing 112 atoms, the state where a germanium atom occupies a cationic position is the most stable. Impurity atoms, as well as impurity atoms and vacancies, show a weak tendency for association. Formation of a singular surface is accompanied by differential relaxation. The charge state of germanium atoms in the bulk and at the surface is virtually the same and somewhat decreases upon association with vacancies.     

Activation of molecular hydrogen on platinum nanoparticles: Quantum-chemical modeling

The interaction of molecular hydrogen with platinum clusters of different size has been modeled by the density functional theory method within the generalized gradient approximation (GGA). The cluster size turns out to have little effect on the interaction energy, whereas the effect of the cluster structure is rather significant. The most efficient interaction with hydrogen is observed for clusters with a structure resembling the crystal structure of platinum metal. In such clusters, the hydrogen molecule is attached to its surface without a barrier. Configurations with the bidentate hydrogen coordination are the most stable ones. The H atoms can migrate over the cluster surface, overcoming moderate potential barriers of ∼0.3–0.4 eV.     

Mass-spectrometric and quantum-chemical investigation of thermochemical characteristics of chlorine oxides

An electron impact technique has been used for the direct determination of the ionization potential (IP) of the ClO₃ radical and the electron affinity (EA) of the ClO₃ and ClO₄ radicals. By means of quantum-chemical calculations taking into account configuration interaction within the framework of the third-order perturbation theory of Miller and Plesset, it has been shown that, for this class of compounds, upon ionization, there are no significant excess energies related to processes of isomerization and electronic excitation. The theoretical and experimental values of the IP and EA are in agreement within 0.5 eV.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2278–2282, October, 1989.     

Quantum-Chemical Modeling of the Surface Contact of Superionic Conductor Li<Subscript>10</Subscript>GeP<Subscript>2</Subscript>S<Subscript>12</Subscript> with Different Materials

The bulk and surface of crystalline lithium-ion conductor Li₁₀GeP₂S₁₂ have been modeled by the density functional theory method in the generalized gradient approximation (GGA). It has been found that barriers to the migration of cations are small both along and across the unit cell, and that in this compound, ionic conductivity is possible in three dimensions. Modeling of the crystal surface has shown that it has a “bumpy” structure and poorly contacts with “hard” crystalline surfaces. With liquid electrolytes (for example, DMSO), such problems do not arise, and lithium cations can pass from one electrolyte to another without overcoming significant potential barriers. Upon contact with metallic lithium, Li₁₀GeP₂S₁₂ decomposes.     

Quantum-chemical modeling of hypervalent configurations in Se-Te glasses

Interactions of intrinsic and impurity local diamagnetic defects in amorphous selenium doped with tellurium were modeled in the cluster approximation with inclusion of electron correlation at the second-order perturbation theory (MP2) level. It was shown that formation of fourfold coordinated hypervalent configurations involving Se and Te atoms is significantly energetically favorable, and the local region energy can be 1 eV lower than the energy of the surrounding region composed of ??normal?? two-coordinate selenium atoms simulating the continuous random network of glass.