The electronic band structure of polydiacetylenes with second- and third-neighbor hopping interaction

2001 ◽  
Vol 79 (4) ◽  
pp. 749-756
Author(s):  
H F Hu ◽  
Y B Li ◽  
K L Yao
Keyword(s):  
Band Structure ◽  
Energy Band ◽  
Energy Gap ◽  
Electronic Band Structure ◽  
Energy Band Structure ◽  
Interaction Parameters ◽  
Energy Bands ◽  
Electronic Band

We have studied the energy band structure of polydiacetylenes (PDAs) using the extensional Hückel Hamiltonian that includes the nonnearest-neighbor hopping interactions. The results show that with increase in the nonnearest-neighbor hopping interaction parameters ρ1 and ρ2, (i) the energy band symmetry is broken and the energy gap 2Δ has changed, (ii) the locations and the widths of energy bands have changed and their shifts depend mainly on ρ1 (next-neighbor hopping interactions), and (iii) the energy gap 2Δ depends mainly on ρ2 (third-neighbor hopping interactions), the effects of the nonnearest-neighbor hopping interaction on the band structure are discussed. PACS No.: 31.15Ct

EFFECTS OF NEXT-NEAREST-NEIGHBOR HOPPING INTERACTION ON THE STRUCTURE OF ELECTRONIC ENERGY BANDS OF POLYDIACETYLENES

1996 ◽  
Vol 10 (19) ◽  
pp. 931-937 ◽  
Author(s):  
H.F. HU ◽  
K.L. YAO
Keyword(s):  
Band Structure ◽  
Electronic State ◽  
Energy Band ◽  
Nearest Neighbor ◽  
Energy Gap ◽  
Electronic Energy ◽  
Energy Band Structure ◽  
Energy Bands ◽  
Extensional Model ◽  
Electronic Energy Bands

Starting from the extensional model Hückel Hamiltonian containing the next-neighbor hopping interactions, the energy band structure and their variation have been studied for polydiacetylenes (PDA’s). With the increase of the next-neighbor hopping interaction parameter ρ the results show that: (1) the electronic state symmetry is broken, (2) the locations and the widths of energy bands have been changed, and (3) the energy gap becomes narrower and the total bandwidth broader. Finally, the effect of the nextneighbor hopping interactions on the band-structure is discussed.

scholarly journals Energy band structure of multistream quantum electron system

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
M. Akbari-Moghanjoughi
Keyword(s):  
Band Structure ◽  
Energy Band ◽  
Mode Coupling ◽  
Electrostatic Interactions ◽  
Electronic Band Structure ◽  
Reciprocal Lattice ◽  
Electron Gas ◽  
Energy Band Structure ◽  
Band Gaps ◽  
Electronic Band

AbstractIn this paper, using the quantum multistream model, we develop a method to study the electronic band structure of plasmonic excitations in streaming electron gas with arbitrary degree of degeneracy. The multifluid quantum hydrodynamic model is used to obtain N-coupled pseudoforce differential equation system from which the energy band structure of plasmonic excitations is calculated. It is shown that inevitable appearance of energy bands separated by gaps can be due to discrete velocity filaments and their electrostatic mode coupling in the electron gas. Current model also provides an alternative description of collisionless damping and phase mixing, i.e., collective scattering phenomenon within the energy band gaps due to mode coupling between wave-like and particle-like oscillations. The quantum multistream model is further generalized to include virtual streams which is used to calculate the electronic band structure of one-dimensional plasmonic crystals. It is remarked that, unlike the empty lattice approximation in free electron model, energy band gaps exist in plasmon excitations due to the collective electrostatic interactions between electrons. It is also shown that the plasmonic band gap size at first Brillouin zone boundary maximizes at the reciprocal lattice vector, G, close to metallic densities. Furthermore, the electron-lattice binding and electron-phonon coupling strength effects on the electronic band structure are discussed. It is remarked that inevitable formation of energy band structure is a general characteristics of various electromagnetically and gravitationally coupled quantum multistream systems.

The Energy Band Structure of Polyacene with Soliton Excitation

1997 ◽  
Vol 11 (11) ◽  
pp. 477-483 ◽  
Author(s):  
Z. J. Li ◽  
H. B. Xu ◽  
K. L. Yao
Keyword(s):  
Band Structure ◽  
Charge Density ◽  
Energy Band ◽  
Energy Gap ◽  
Electronic States ◽  
Energy Band Structure ◽  
Energy Spectra ◽  
Energy Band Gap ◽  
The One ◽  
Soliton Excitation

Starting from the extensional Su–Schrieffer–Heeger model taking into account the effects of interchain coupling, we have studied the energy spectra and electronic states of soliton excitation in polyacene. The dimerized displacement u0 is found to be similar to the case of trans-polyacetylene, and equals to 0.04 Å. The energy-band gap is 0.38 eV, in agreement with the results derived by other authors. Two new bound electronic states have been found in the conduction band and in the valence band, which is different from the one of trans-polyacetylene. There exists two degenerate soliton states in the center of energy gap. Furthermore, the distribution of charge density and spin density have been discussed in detail.

Energy band structure of Cd3P2 for real D4h15 symmetry I. Energy bands

1979 ◽  
Vol 92 (2) ◽  
pp. 379-387 ◽  
Author(s):  
P. Plenkiewicz ◽  
B. Dowgiałło-Plenkiewicz
Keyword(s):  
Band Structure ◽  
Energy Band ◽  
Energy Band Structure ◽  
Energy Bands

Study on the Energy Band Structure of La Doped ZnO

2011 ◽  
Vol 233-235 ◽  
pp. 2119-2124
Author(s):  
Xiao Qing Liu ◽  
Rui Fang Zhang ◽  
Yi Guo Su ◽  
Xiao Jing Wang
Keyword(s):  
Band Structure ◽  
Conduction Band ◽  
Energy Band ◽  
Density Functional ◽  
Energy Band Structure ◽  
Partial Density ◽  
Energy Bands ◽  
Doped Zno ◽  
Zno Crystal ◽  
La Doped

The energy bands of La -doped ZnO were studied systematically by the density functional theory (DFT). Based on the data of the band structure, DOS (Density of State) and PDOS( Partial Density of States), atomic populations and net charge, the influence on the energy band structure of the macrostructure of ZnO and La-doped ZnO was investigated. The results showed that the free electrons were produced by the doping of La on (or in) ZnO crystal. The Fermi energy was shifted up to the conduction band, making the ZnO particles having the characters of degenerated semiconductor. The excitation from impurity states to the conduction band may account for the blue shift of the absorption edge in the model of La-doped ZnO. Comparison with the different models of the La doped/loaded on the ZnO surface, La atoms loaded on the surface of ZnO and La atoms replaced of Zn atoms on the ZnO surface, the shift to the lower energy location were found after La doping/loading. The more shift and the large band gap was found for the model of La doped on the Zn position in the ZnO crystal.

scholarly journals Динамика решетки и электронные свойства нелинейного кристалла BaGa-=SUB=-2-=/SUB=-GeS-=SUB=-6-=/SUB=-: комбинационное рассеяние, ИК отражение и расчет ab initio

2019 ◽  
Vol 127 (7) ◽  
pp. 20
Author(s):  
С.А. Климин ◽  
Б.Н. Маврин ◽  
И.В. Будкин ◽  
В.В. Бадиков ◽  
Д.В. Бадиков
Keyword(s):  
Band Structure ◽  
Energy Gap ◽  
Electronic Band Structure ◽  
Potential Method ◽  
Dispersion Analysis ◽  
Reflection Spectra ◽  
Electronic Band ◽  
Ir Reflection ◽  
Ir Reflection Spectra ◽  
Polarized Raman

AbstractWe have measured the polarized Raman scattering and IR reflection spectra of a BaGa_2GeS_6 crystal, the Ga and Ge atoms of which are disordered, randomly occupying crystallographic positions of the same kind. The IR reflection spectra have been processed by the dispersion analysis method. The dispersion of phonons, the density of phonon states, the electronic band structure, and the partial densities of electronic states have been calculated in the DFT approximation using the alchemical potential method for disordered Ga and Ge atoms. It has been found that the stretching vibrations in the vibrational spectra are separated from the bending modes by a gap of about 100 cm^–1 and that the band structure of the crystal has an indirect energy gap.

COUPLED EFFECT OF STRAIN AND MAGNETIC FIELD ON ELECTRONIC BAND STRUCTURE OF GRAPHENE

2011 ◽  
Vol 10 (01n02) ◽  
pp. 345-349 ◽  
Author(s):  
YASHUDEEP SINGH ◽  
D. ROY MAHAPATRA
Keyword(s):  
Magnetic Field ◽  
Energy Spectrum ◽  
Band Structure ◽  
Energy Gap ◽  
Electronic Band Structure ◽  
Unified Framework ◽  
Electronic Band ◽  
Energy Bandgap ◽  
Threshold Strain ◽  
Coupled Effect

Hofstadter's fractal energy spectrum, which is also called Hofstadter butterfly, remained as one of the most interesting topics of condensed matter physics for decades. We study, in this paper, how different patterns of energy spectrum emerge when a graphene sheet is subjected to in-plane uniaxial and shear strain in the presence of transverse magnetic field. We discuss these patterns in the context of opening of the electronic energy band structure of graphene. We thus provide a unified framework for graphene under the coupled effect of strain and magnetic field. Due to such coupling, the energy bandgap opens when certain threshold of strain in the zigzag direction of graphene is crossed. The threshold strain value depends on the rationality of the parameter ϕ/ϕo, i.e., the ratio of magnetic flux through the deformed hexagonal plaquette and the quantum flux (h/e). Numerical results shows that the energy bandgap depends nonlinearly on the magnitude of strain, and that the threshold strain and energy gap decrease with decreasing magnetic field.

The electronic band structure of PbS

1953 ◽  
Vol 217 (1128) ◽  
pp. 71-91 ◽  
Keyword(s):  
Band Structure ◽  
Energy Gap ◽  
Electronic Band Structure ◽  
Optical Transition ◽  
Wave Length ◽  
Rate Of Change ◽  
Wave Functions ◽  
Least Square ◽  
Electronic Band ◽  
Cellular Method

The cellular method has been applied to the determination of electronic wave functions of the Bloch type in PbS. In each cell ψ is expanded in terms of ‘Kubic harmonics', and a table of these functions (for a NaCl type of lattice) for prominent points in momentum space is included. An attempt has been made to establish a self-consistent field, by treating only the electrons with k = 0, but results have shown that this approximation is not very good. Methods of matching the wave functions at the boundaries between the cells are described, based either on least square fitting or on expansion of ψ in terms of functions which are orthogonal over the boundaries. These methods have been tested with the empty lattice test. Curves are given showing the approximate band structure in two prominent crystallographic directions. The resulting width of the full band is about 6 eV, that of the conduction band about 7 eV. The forbidden energy gap is very small (< 0.3 eV). The lowest allowed optical transition has a wave-length of 0.9 μ. These results are in agreement with the observed absorption spectrum and suggest that its tail is due to forbidden transitions. The calculated rate of change with temperature of the energy gap is 2 x 10 -4 eV /degree, about half the experimental value.

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