scholarly journals Fermi surface electron–hole instability of the (TMTSF)2PF6 Bechgaard salt revealed by the first-principles Lindhard response function

2020 ◽  
Vol 32 (34) ◽  
pp. 345701
Author(s):  
Bogdan Guster ◽  
Miguel Pruneda ◽  
Pablo Ordejón ◽  
Enric Canadell ◽  
Jean-Paul Pouget
Keyword(s):  
Fermi Surface ◽  
Response Function ◽  
First Principles ◽  
Surface Electron ◽  
Electron Hole ◽  
Bechgaard Salt

First-Principles Study on Electronic and Optical Properties in Pr-Doped Anatase TiO2

2014 ◽  
Vol 924 ◽  
pp. 260-268 ◽  
Author(s):  
Hao Chen ◽  
Lan Fang Yao ◽  
Song Lin Yang ◽  
Ya Qin Wang ◽  
Xing Liang ◽  
...  
Keyword(s):  
Optical Properties ◽  
Photocatalytic Activity ◽  
First Principles ◽  
Energy Gap ◽  
Impurity Band ◽  
Anatase Tio2 ◽  
Electron Hole ◽  
Light Region ◽  
Overlap Population ◽  
Calculation Results

The crystal structures, band structures, density of states, charge density, overlap population and optical properties of pure anatase TiO2 and Pr-doped anatase TiO2 were studied by using the plane-wave pseudopotential method based on the first-principles. After Pr doping, the valence band and the conduction band moved down and became dense, energy gap became narrow and a impurity band which consists of Pr 4f states appeared. And the dipole moment got improved, which is good for the separate of the electron-hole pairs. These effectively overcome two huge shortcomings of TiO2. Besides, Pr-doped anatase TiO2 produced more carriers which have good transport properties and the absorption spectra of Pr-O bond appear in the region that the wavelength is longer. The calculation results of optical properties show that the absorption edge occured red shift, which means the photocatalytic activity of anatase TiO2 got remarkable improved during visible-light region. This conforms to the previous analysis. So the photocatalytic activity of anatase TiO2 got remarkable improved after Pr doping.

The dependence of the hyperfine interaction on the cellular potential in Na and K. II

1969 ◽  
Vol 47 (13) ◽  
pp. 1331-1336 ◽  
Author(s):  
R. A. Moore ◽  
S. H. Vosko
Keyword(s):  
Fermi Surface ◽  
Electron Density ◽  
Wave Functions ◽  
Electron Wave ◽  
Surface Electron ◽  
Conduction Electrons ◽  
Hartree Fock ◽  
A Value ◽  
Dependent Potential ◽  
Conduction Electron Density

The dependence of the Fermi surface electron wave functions in Na and K on (i) an L-dependent effective local cellular potential constructed to simulate Hartree-Fock theory and (ii) the inclusion of the Hartree field due to the conduction electrons in the cellular potential is investigated. All calculations are performed using the Wigner–Seitz spherical cellular approximation and the Schrödinger equation is solved by the Kohn variational method. It is found that to ensure a value of the Fermi surface electron density at the nucleus accurate to ~5%, it is necessary to use the L-dependent potential along with the Hartree field due to a realistic conduction electron density.

Dynamical interaction of surface electron-hole pairs with surface defects: Surface spectroscopy monitored by particle emissions

1993 ◽  
Vol 70 (16) ◽  
pp. 2495-2498 ◽  
Author(s):  
Jun’ ichi Kanasaki ◽  
Akiko Okano ◽  
Ken’ ichi Ishikawa ◽  
Yasuo Nakai ◽  
Noriaki Itoh
Keyword(s):  
Surface Defects ◽  
Surface Electron ◽  
Electron Hole ◽  
Particle Emissions ◽  
Dynamical Interaction ◽  
Surface Spectroscopy

scholarly journals New MAX Phase Superconductor Ti2GeC: A First-principles Study

2013 ◽  
Vol 6 (1) ◽  
pp. 11-27 ◽  
Author(s):  
M. A. Hadi ◽  
M. Roknuzzaman ◽  
F. Parvin ◽  
S. H. Naqib ◽  
A. K. M. A. Islam ◽  
...  
Keyword(s):  
Optical Properties ◽  
Thermodynamic Properties ◽  
Fermi Surface ◽  
Vickers Hardness ◽  
First Principles ◽  
Elastic Anisotropy ◽  
Debye Model ◽  
First Principles Calculation ◽  
Max Phase ◽  
Specific Heats

This is the first DFT-based first-principles prediction of the detailed optical and thermodynamic properties, including Vickers hardness and Fermi surface of 211 MAX phase Ti2GeC for which superconductivity (Tc~ 9.5 K) was reported very recently. The calculated structural properties are in excellent agreement with experiments. Our results on elastic parameters indicate a slight elastic anisotropy and brittleness of the compound. The chemical bonding is seen to be a combination of covalent, ionic and metallic nature. The rather stronger covalent bonding is responsible for its high Vickers hardness of 11.6 GPa. The investigated Fermi surface is formed mainly by the low-dispersive bands, which should be responsible for the presence of superconductivity in Ti2GeC. All the optical properties are evaluated and analyzed for two different polarization directions of incident photon. The temperature and pressure dependence of primitive cell volume, thermal expansion coefficient, specific heats, bulk modulus, and Debye temperature of Ti2GeC are derived from the quasi-harmonic Debye model with phononic effect and the various implications are discussed in details.  Keywords: First-principles calculation; Vickers hardness; Optical properties; Thermodynamic properties. © 2014 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. doi: http://dx.doi.org/10.3329/jsr.v6i1.16604 J. Sci. Res. 6 (1), 11-27 (2014)

First-Principles Study of Optical Excitations in Alpha Quartz

1999 ◽  
Vol 579 ◽  
Author(s):  
Eric K. Chang ◽  
Michael Rohlfing ◽  
Steven G. Louie
Keyword(s):  
Absorption Spectrum ◽  
First Principles ◽  
Optical Spectrum ◽  
Quantitative Description ◽  
Frequency Range ◽  
Gw Approximation ◽  
Electron Hole ◽  
Self Energy ◽  
Excitonic Effects

ABSTRACTThe properties of silicon dioxide have been studied extensively over the years. However, there still remain major unanswered questions regarding the nature of the optical spectrum and the role of excitonic effects in this technologically important material. In this work, we present an ab initio study of the optical absorption spectrum of alpha-quartz, using a newly developed first-principles method which includes self-energy and electron-hole interaction effects. The quasiparticle band structure is computed within the GW approximation to obtain a quantitative description of the single-particle excitations. The Bethe-Salpeter equation for the electron-hole excitations is solved to obtain the optical spectrum and to understand the spatial extent and physical properties of the excitons. The theoretical absorption spectrum is found to be in excellent agreement with the measured spectrum. We show that excitonic effects are crucial in the frequency range up to 5 eV above the absorption threshold.

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