Surface structure and energy of B2 type intermetallic compound NiAl

The surface structure and energies for 22 surfaces of NiAl, an ordered intermetallic compound of B2 structure, have been studied by using embedded atom method. The results show that, for alternating Ni and Al surfaces with odd numbers of the sum of their three Miller indices, the energy difference between the Ni terminated surface and Al terminated surface increase linearly with increasing the interlayer distance. So from surface energy minimization, the Al terminated surface is favorable for each alternating Ni and Al surface. This is in agreement with experimental results. However, the energy of the (1 1 0) surface belonged to the other kind of the surface consisted of stoichiometric atomic layers and with even numbers of the sum of their three Miller indices, is the lowest in all two kinds of the surfaces. Therefore the (1 1 0) texture of NiAl appears mostly in the experiments.     

Electronic structure of CsAu

Self-consistent non-relativistic and relativistic LMTO band structure calculations have been carried out for CsAu. In the non-relativistic model CsAu is a metal, whereas — in agreement with experiments — the relativistic calculations predict CsAu to be a semiconductor. The gap is not caused by the spin-orbit coupling. The importance of the core-like Cs-5s and Cs-5p states for the alloy formation is discussed, and charge distribution calculations are used to illustrate the ionic nature of the bonding.     

Electronic structure of Ce-pnictides

High-resolution x-ray photoemission has been used to study the electronic structure of the Ce-pnictides (CeN, CeP, CeAs and CeSb). This series of isostructural compounds allows us to follow the evolution of the 4f level as the distance between Ce atoms varies. Core level spectra show clearly that the 4f state is localized in all the compounds. In the valence band region, the width of the 4f peak is strongly influenced by the energy overlap with the extended states originating from anion p states. The spectra of CeN reveal the existence of a mixed configuration.     

Electronic structure of CsAu

X-ray photoemission spectra of CsAu prepared in vacuum are in good agreement with the ionic character expected for this material. The Cs 5p doublet lies well below flat Au 5d bands. The Au 6s valence band is located somewhat closer to the 5d states than recent band structure calculations indicate. The charge transfer to gold is in the range 0.6 to 0.8 electrons.     

The effect of boron on the electronic structure of dislocation in NiAl

The segregation effect of B on the [100](010) edge dislocation core in NiAl single crystals is investigated using the DMol method and the discrete variational method within the framework of density functional theory. The impurity segregation energy and the charge distribution are calculated. The effects of B on the dislocation motion are discussed. The results show that B prefers to segregate at the Center-Al dislocation core. Moreover, B forms strong bonding states with its neighboring host atoms, which ma...     

Electronic structure of polyperylene

The electronic structure of polyperylene is studied on the basis of the one-dimensional tight-binding SCF-CO (self consistent field-crystal orbital) method. The geometry of this polymer is optimized from the energetic point of view. The analysis of the electronic properties of polyperylene reveals that this polymer will be a promising member of the one-dimensional graphite as a new electrically conductive or semi-conductive material.     

Electronic structure of SmOFeAs

The electronic structure of SmOFeAs, a parent compound of iron arsenic superconductors, is measured by angle resolved photoemission spectroscopy. Due to the surface contribution, the measured electronic structure deviates strongly from the calculations. One of the bulk bands is identified by photon energy dependence measurements. Moreover, the appearance of sharp quasiparticle peaks at low temperatures implies the drastic reduction of the scattering rate. No energy gap is observed at Fermi level, indicating that the Fermi surface nesting is irrelevant in the spin density wave formation.     

Electronic structure of silicene

In this topical review, we discuss the electronic structure of free-standing silicene by comparing results obtained using different theoretical methods. Silicene is a single atomic layer of silicon similar to graphene. The interest in silicene is the same as for graphene, in being two-dimensional and possessing a Dirac cone. One advantage of silicene is due to its compatibility with current silicon electronics. Both empirical and first-principles techniques have been used to study the electronic properties of silicene. We will provide a brief overview of the parameter space for first-principles calculations.However, since the theory is standard, no extensive discussion will be included. Instead, we will emphasize what empirical methods can provide to such investigations and the current state of these theories. Finally, we will review the properties computed using both types of theories for free-standing silicene, with emphasis on areas where we have contributed.Comparisons to graphene is provided throughout.     

Electronic structure of MnSb

On the basis of a two center tight binding model the recursion method of Haydock et al. was applied to calculate spin polarized and non-polarized electronic densities of states and magnetic moments for the B8₁ crystal structure and a fictitious B32 structure of MnSb. The model implies the itinerant nature of the Mn d-states hybridizing with Sb p-states. For the non-polarized densities of states the self-consistent charge transfer amounts to 0.6 electrons from Mn to Sb with a band center difference of E_p ? E_d = - 0.75 eV. For the magnetic moments, which were also calculated self-consistently, 3.5 μ_B for the d-band and 3.34 μ_B in total were obtained for the B8₁ crystal structure. For the B31 structure bigger moments of 3.67 μ_B and 3.53 μ_B were obtained, correspondingly. The results for MnSb are also discussed with respect to very recent results for MnAs calculated within the same model. The local densities of states as obtained for MnSb are in good agreement with experimental XPS results.     

Electronic structure of solids

A review of progress in calculating properties related to the electronic structure of solids is presented with emphasis on the pseudopotential method.     

Electronic structure of PCBM

We have studied the electronic structure of [6,6]-phenyl-C₆₁-butyric-acid-methyl-ester (PCBM) using synchrotron radiation photoelectron spectroscopy (PES) measurements and first-principles calculations. The PES spectrum of the entire occupied valence band is reported, which exhibits abundant spectral features from the Fermi level to ～24 eV binding energy. All the spectral features are broadened as compared with the cases of C₆₀. The reasons for the broadening are analysed by comparing the experimental data with the calculated energy levels and density of states. Special attention is paid to the analysis of the C₆₀ highest occupied molecular orbital (HOMO)-1 derived states, which can play a crucial role in the bonding at the interfaces of PCBM/polymer blenders or PCBM/electrodes. Besides the well-known energy level splitting of the C₆₀ backbone caused by the lowered symmetry, C 2p states from the side chain mix or hybridize with the molecular orbitals of parent C₆₀. The contribution of the O 2p states can substantially modify the PES spectrum.     

Energetics and electronic structure of refractory elements in the dislocation of NiAl

Using DMol and the discrete variational method within the framework of the density functional theory,we study the alloying effects of Nb,Ti,and V in the [100](010) edge dislocation core of NiAl.We find that when Nb(Ti,V) is substituted for Al in the center-Al,the binding energy of the system reduces 3.00 eV(2.98 eV,2.66 eV).When Nb(Ti,V) is substituted for Ni in the center-Ni,the binding energy of the system reduces only 0.47 eV(0.16 eV,0.09 eV).This shows that Nb(Ti,V) exhibits a strong Al site preference,which agrees with the experimental and other theoretical results.The analyses of the charge distribution,the interatomic energy and the partial density of states show that some charge accumulations appear between the impurity atom and Ni atoms,and the strong bonding states are formed between impurity atom and neighbouring host atoms due mainly to the hybridization of 4d5s(3d4s) orbitals of impurity atoms and 3d4s4p orbitals of host Ni atoms.The impurity induces a strong pinning effect on the [100](010) edge dislocation motion in NiAl,which is related to the mechanical properties of the NiAl alloy.     

Electronic structure of graphite nanopipes

A recursion method is used for calculating the electron-state density n(E) of carbon in diamond, graphite, C₆₀ fullerene, and graphite nanopipes of various structures and diameters. The calculated n(E) for diamond, graphite, and fullerene are compared with experimental data. The distinctive features of the electron-state density n(E) in graphite nanopipes are discussed. Fiz. Tverd. Tela (St. Petersburg) 39, 1118–1121 (June 1997)