Electronic Structure and Optical Absorption of Fluorographene

2011 ◽  
Vol 1370 ◽  
Author(s):  
Yufeng Liang ◽  
Li Yang
Keyword(s):  
Absorption Spectrum ◽  
Electronic Structure ◽  
Charge Transfer ◽  
Optical Absorption ◽  
Optical Absorption Spectrum ◽  
First Principles ◽  
Gw Approximation ◽  
Exciton Condensation ◽  
Excitonic Effects ◽  
Electron Effects

ABSTRACTA first-principles study on the quasiparticles energy and optical absorption spectrum of fluorographene is presented by employing the GW + Bethe-Salpeter Equation (BSE) method with many-electron effects included. The calculated band gap is increased from 3.0 eV to 7.3 eV by the GW approximation. Moreover, the optical absorption spectrum of fluorographene is dominated by enhanced excitonic effects. The prominent absorption peak is dictated by bright resonant excitons around 9.0 eV that exhibit a strong charge transfer character, shedding light on the exciton condensation and relevant optoelectronic applications. At the same time, the lowest-lying exciton at 3.8 eV with a binding energy of 3.5 eV is identified, which gives rise to explanation of the recent ultraviolet photoluminescence experiment.

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.

ENERGY STATES IN QUANTUM DOTS

2002 ◽  
Vol 12 (01) ◽  
pp. 15-43 ◽  
Author(s):  
ANDREW J. WILLIAMSON
Keyword(s):  
Quantum Dots ◽  
Absorption Spectrum ◽  
Electronic Structure ◽  
Optical Absorption ◽  
Configuration Interaction ◽  
Single Particle ◽  
Optical Absorption Spectrum ◽  
Semiconductor Quantum Dots ◽  
Binding Energies ◽  
Particle Level

We describe a procedure for calculating the electronic structure of semiconductor quantum dots containing over one million atoms. The single particle electron levels are calculated by solving a Hamiltonian constructed from screened atomic pseudopotentials. Effects beyond the single particle level such as electron and hole exchange and correlation interactions are described using a configuration interaction (CI) approach. Application of these methods to the calculation of the optical absorption spectrum, Coulomb repulsions and multi-exciton binding energies of InGaAs self-assembled quantum dots are presented.

Effect of cation off-stoichiometry on optical absorption in epitaxial LaFeO3 films

2017 ◽  
Vol 19 (16) ◽  
pp. 10371-10376 ◽  
Author(s):  
Mark D. Scafetta ◽  
Steven J. May
Keyword(s):  
Absorption Spectrum ◽  
Electronic Structure ◽  
Optical Absorption ◽  
Optical Absorption Spectrum ◽  
Defect Chemistry ◽  
Epitaxial Films ◽  
Perovskite Oxide ◽  
Cation Deficiency ◽  
The Relationship

The effect of A- and B-site cation deficiency on the optical absorption spectrum is presented for a series of LaFeO3−δ epitaxial films providing insights into the relationship between defect chemistry and electronic structure in this semiconducting perovskite oxide.

CLUSTER CALCULATION OF THE ELECTRONIC STRUCTURE OF K3C60

1995 ◽  
Vol 09 (02) ◽  
pp. 95-101 ◽  
Author(s):  
KALINE COUTINHO ◽  
SYLVIO CANUTO ◽  
A. FAZZIO ◽  
R. MOTA
Keyword(s):  
Absorption Spectrum ◽  
Electronic Structure ◽  
Optical Absorption ◽  
Density Of States ◽  
Optical Absorption Spectrum ◽  
Cluster Calculation ◽  
Metallic System ◽  
Calculated Density ◽  
Inverse Photoemission ◽  
Molecular Orbital Model

A cluster with 188 atoms is utilized to investigate the electronic structure of K 3 C 60 within the molecular orbital model. The calculated density of states is in excellent agreement with experimental results of photoemission and inverse photoemission. The band gap is calculated using three different schemes and the results indicate a metallic system. The optical absorption spectrum is calculated from a CI procedure and indicates transitions below 15000 cm –1 not present in pristine C 60.

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