Theoretical photoelectronic spectra of molybdenum, tungsten, and rhenium disilicides

Photoelectronic spectra of volume samples of molybdenum, tungsten, and rhenium disilicides are theoretically investigated as functions of the excitation energy (hv = 12–1486 eV) by the method of linearized attached plane waves. The main contribution to the spectrum at low (hv = 12–52 eV) and very high (hv = 1486 eV) excitation energies is given by the metal d-states, while the contribution of the Si p-states is dominant at intermediate excitation energies. An analysis of the calculated results demonstrates that the main peak of the photoelectronic spectra is displaced by 0.2 eV toward the bottom of the valence band when going from MoSi₂ to WSi₂; it is displaced by 0.3 eV when going from WSi₂ to ReSi_1.75. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 75–80, July, 2006.     

Quantum-chemical modeling of the structure of strained silicon nanocrystals on a germanium substrate

The results of optimization of the atomic and electronic structure of strained silicon clusters Si₅₁ on a germanium substrate are presented. The interaction of boundary nanocluster atoms with the substrate is studied. The effect of strain and impurities on the distribution of electronic states is analyzed.     

Spatial and electronic structures of the germanium-tantalum clusters TaGe n − (n = 8–17)

The results of optimizing the spatial structure and calculated electronic spectra of the TaGe _n ^? anion clusters (n = 8–17) have been presented. The calculations have been performed in terms of the density functional theory. The most probable spatial structures of clusters detected in the experiment have been determined by comparing the calculated and available experimental data.     

Electronic structure of cobalt disilicide film

The electronic structure of cobalt disilicide film has been investigated theoretically. The calculations are performed within the framework of the linearized augmented plane wave method. A combined analysis of the total and local partial densities of states and the photoelectron and x-ray emission spectra of different series for all the nonequivalent atoms of the film makes it possible to interpret the main features of the spectral characteristics of this material.     

Electronic structure of FeSi<Subscript>2</Subscript>

The electronic structure of volume and film iron disilicides with crystal structure of the type of α leboit and fluorite was calculated using the linearized augmented plane-wave formalism. Joint and local partial densities of electronic states, x-ray emission spectra in different series of all inequivalent atoms of these phases, and photoelectron spectra for different excitation energies were obtained. γ-FeSi₂ was found to be, unlike α-FeSi₂, an unstable phase in both the volume and film realizations. X-ray L _2,3 emission spectra of silicon in the iron group disilicides NiSi₂, CoSi₂, and FeSi₂ were compared. NiSi₂, CoSi₂, and α-FeSi₂ exhibit transformation of the maximum in the near-Fermi region of the Si L _2,3 spectra as one crosses over from a bulk to a film sample. This transformation is closely connected with phase stability and may serve as a criterion of thermodynamic stability of the iron-group transition-metal disilicides.     

Fermi surface and electrical characteristics of molybdenum disilicide

Semirelativistic self-consistent calculations of the electronic structure of MoSi₂ are performed within the framework of the linearized augmented-plane-wave (APW) method in the local density functional approximation. The results of investigations of the band structure, the Fermi surface, and electrical characteristics (effective cyclotron masses, the conductivity anisotropy constant, the mean free path, and the coefficient γ of the heat capacity component linear in temperature) are reported. The Fermi surface consists of two sheets, namely, an electron sheet and a hole sheet. The extreme sectional areas of the Fermi surface agree well with the experimental data on the de Haas-van Alphen effect. The results of first-principles calculations need no additional correction.     

Influence of the special features of atomic structure of Si24 and MeSi24 (Me = Na or K) nanoparticles on their electron properties

The influence of atomic structure of silicon nanoparticles on the distribution of total and partial state densities in the valence and conductivity bands as well as on the valence band and gap widths is analyzed based on the calculated geometrical and electron structure of the Si ₂₄ and MeSi ₂₄ (Me = Na or K) clusters. Semi-empirical AM1 and PM3 methods are used for calculations. The adequacy of calculations is confirmed by their comparison with the available experimental data. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 46–51, February, 2006.     

Spatial structure and electronic spectrum of TiSi n − clusters (n = 6–18)

Results from optimizing the spatial structure and calculated electronic spectra of anion clusters TiSi _n ^? (n = 6–18) are presented. Calculations are performed within the density functional theory. Spatial structures of clusters detected experimentally are established by comparing the calculated and experimental data. It is shown that prismatic and fullerene-like structures are the ones most energetically favorable for clusters TiSi _n ^? . It is concluded that these structures are basic when building clusters with close numbers of silicon atoms.