Lifetimes of electronic excitations in unoccupied surface states and the image potential states on Pd(110)

The contribution of inelastic electron-electron scattering to the decay rate of excitations in the surface states and first two image potential states at the ? point on the surface is calculated in the GW approximation, and the quasi-momentum dependence of the corresponding contribution for the surface states is analyzed. The mechanisms of electron scattering in these states are studied, and the temperature dependence of the excitation lifetime is analyzed with allowance for the contribution of the electron-phonon interaction calculated earlier.     

Three- and two-dimensional topological insulators in Pb2Sb2Te5, Pb2Bi2Te5, and Pb2Bi2Se5 layered compounds

The electronic structure of ternary compounds Pb₂Sb₂Te₅, Pb₂Bi₂Te₅, and Pb₂Bi₂Se₅, which have a layered structure that consists of nine-layer atomic blocks separated by van der Waals gaps, has been theoretically studied. It has been shown that all studied compounds are three-dimensional topological insulators. The possibility of the existence of a two-dimensional topological insulator has been found in ultrathin (0001) Pb₂Sb₂Te₅ and Pb₂Bi₂Te₅ films. Oscillations of the ℤ₂ topological invariant with an increase in the film thickness have been observed in the latter compound.     

Ternary compounds based on binary topological insulators as an efficient way for modifying the Dirac cone

The electronic structure of A^IVB^VI · A₂^VB₃^VI ternary compounds consisting of seven-layer atomic blocks separated by van der Waals gaps has been theoretically investigated. The YbBi(Sb)2Te₄ compounds have been considered, for which a similar atomic structure has been predicted. It has been shown that most compounds based on Group IV elements, as well as YbBi₂Te₄, are three-dimensional topological insulators. Calculations of the surface electronic structure of MBi₂Te₄, where M is a Group IV element or Yb, demonstrate the possibility of tuning the Dirac surface conduction state owing to the first element.     

Promoting of non-transition metal alkylation with organyl halides in the presence of binary systems based on an organometallic compound and a transition metal compound: I. Hypothetical stepwise scheme and verification of the system efficiency

A hypothetical scheme has been proposed for the alkylation of non-transition metals with organyl halides in the presence of binary systems consisting of an organometallic compound and a transition metal compound. The scheme implies catalysis by transition metal atoms, small clusters, and subhalides adsorbed on the surface of metal to be alkylated. These particles are formed during the process as a result of interaction between the binary system components. The alkylation of commercial zinc powder with ethyl bromide has been used as a model reaction to demonstrate that the binary system ethylzinc bromide-copper(I) iodide is superior in its efficiency and experimental simplicity to all other examined methods for stimulation of the alkylation of elements with organyl halides yielding organometallic compounds.     

Dimers of heavy <Emphasis Type="Italic">p</Emphasis>-elements of groups IV–VI: Electronic,vibrational, and magnetic properties

Equilibrium lengths and binding energies, vibrational frequencies, width of the HOMO–LUMO gap, and the magnetic anisotropy energies for one- and two-component dimers of heavy p elements of Groups IV (Sn, Pb), V (Sb, Bi), and VI (Se, Te) with a pronounced relativistic effect have been calculated with the use of the formalism of the density functional theory. It has been shown that it is necessary to take into account the spin–orbit coupling, which significantly affects the energy parameters of clusters. The analysis of the data obtained has revealed that the Pb–Te, Pb–Se, Sn–Te, and Sn–Se dimers have the widest gap at the Fermi level and the lowest reactivity. The magnetic anisotropy energy has been calculated for all single- and doublecomponent dimers and the direction of the easy magnetization axis has been determined.