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The band structure calculations were made for RMn compounds, where R is a rare-earth element, M = Fe and Co, and n = 2, 3, 23/6 and 17/2. For each series, the magnetic moments of the transition metals linearly depend on the de Gennes factor with rates determined by their local environment. Exchange interactions are analyzed starting with the 4f–5d–3d model. The contributions of local 4f–5d interactions, as well as 5d–3d short-range interactions, to the polarization M5d of R5d band is determined. Exchange interactions at unit cell level are interdependent and mediated by the R5d band polarization. A linear dependence of the Curie temperatures on the M5d values is shown for each RMn series. The results are discussed in correlation with the experimental data obtained by magnetic and neutron diffraction measurements. [ABSTRACT FROM AUTHOR]

In this paper, some electronic properties such as the electronic density of states (DOS), and energy band structure, and optical properties of the bulk and monolayer PtSe2 structure have been investigated based on the density functional theory (DFT) using full-potential linearized augmented plane wave (FP-LAPW) method and the modified Becke-Johnson potential (mBJ). By changing the PtSe2 structure size from bulk to monolayer, there have been major changes in the electronic (DOS and band structure) and optical properties such as the dielectric function. The electronic results show that PtSe2 in the bulk state exhibits a metallic property, while its nanosheet state, PtSe2 is a semiconductor with an energy gap of about 1.5 eV. Band structure calculations showed that for PtSe2 structure in the bulk state the energy distance between Γ-point and the K-point is about 0.4 eV, so it is concluded that PtSe2 is a semi-metal. The optical properties results show that the largest damping region for electromagnetic waves for a bulk PtSe2 structure in the z-direction is equal to 14.02 eV. The volume plasmon energy of the PtSe2 monolayer is smaller than the plasmon energy of the bulk PtSe2. Also, the optical reflectivity of the bulk PtSe2 is larger than the optical reflectivity of the PtSe2 monolayer. [ABSTRACT FROM AUTHOR]

In this paper, some electronic properties such as the electronic density of states (DOS), and energy band structure, and optical properties of the bulk and monolayer PtSe2 structure have been investigated based on the density functional theory (DFT) using full-potential linearized augmented plane wave (FP-LAPW) method and the modified Becke-Johnson potential (mBJ). By changing the PtSe2 structure size from bulk to monolayer, there have been major changes in the electronic (DOS and band structure) and optical properties such as the dielectric function. The electronic results show that PtSe2 in the bulk state exhibits a metallic property, while its nanosheet state, PtSe2 is a semiconductor with an energy gap of about 1.5 eV. Band structure calculations showed that for PtSe2 structure in the bulk state the energy distance between Γ-point and the K-point is about 0.4 eV, so it is concluded that PtSe2 is a semi-metal. The optical properties results show that the largest damping region for electromagnetic waves for a bulk PtSe2 structure in the z-direction is equal to 14.02 eV. The volume plasmon energy of the PtSe2 monolayer is smaller than the plasmon energy of the bulk PtSe2. Also, the optical reflectivity of the bulk PtSe2 is larger than the optical reflectivity of the PtSe2 monolayer. [ABSTRACT FROM AUTHOR]

Tight-binding calculations with an extended Hückel Hamiltonian were performed on BaPtB and LuOsB. Hypothetical linear metal boride chains present in these materials are analyzed with a three-dimensional model that contains a trigonal bipyramidal TB (T = transition metal) building unit for the compounds. The geometrical structure for the TB trigonal bipyramids depends on the number of electrons. For systems that have greater than 36 electrons in its trigonal bipyramidal building unit, a structural distortion is expected. Electron back donation from the electron-rich M fragment to the empty e′ set on B creates boron-boron interaction along the z-axis. Boron-boron pairing then participates as an electron sink and causes a trigonal distortion of the platinum Kagome net. On the other hand, a system with <35 electrons should have an undistorted, CeCoB type structure. The electronic factors that create the breathing motion are discussed and analyzed with the aid of molecular and solid-state models. The metal-metal bonding associated with the structural properties also has been examined. [ABSTRACT FROM AUTHOR]

We have carried out an extensive study of electronic properties of silver iodide in β- and γ-phases. The theoretical Compton profiles, energy bands, density of states and anisotropies in momentum densities are computed using density functional theories. We have also employed full-potential linearized augmented plane-wave method to derive the energy bands and the density of states. To compare our theoretical data, isotropic Compton profile measurement on γ-AgI using Cs Compton spectrometer at an intermediate resolution of 0.38 a.u. has been undertaken. The theoretical anisotropies are also interpreted on the basis of energy bands. [ABSTRACT FROM AUTHOR]

Based on FLAPW-GGA calculations, a comparative study of the features of interatomic interactions in LaFeAsO, SrFe2As2, and LiFeAs layered crystals (basic phases of new 18–56 K superconductors) is carried out. [ABSTRACT FROM AUTHOR]

In this paper, a new design and construction of a low intensity (100 mCi) 241Am γ-ray Compton spectrometer is presented. The planar spectrometer is based on a small disc source with the shortest geometry. Measurement of the momentum density of polycrystalline Al is used to evaluate the performance of the new design. The measured profile is in good agreement with the existing theoretical data and our density functional calculations. [ABSTRACT FROM AUTHOR]

The electronic band structure and stability of extended nanocrystallites (NCs) of titanium monocarbide TiC were investigated by the electron density functional-tight binding (DFTB) technique. The stability of prismatic NCs increases with the number of atomic layers; the electronic spectrum of these compounds changes from semiconductor (for NC of minimal atomic size) to metallike type inherent in crystalline titanium carbide. [ABSTRACT FROM AUTHOR]