Pros and cons of time-dependent hybrid density functional approach to optical spectra of solids: a case study of CeO2

Author(s):  
Huai-Yang Sun ◽  
Shuo-Xue Li ◽  
Hong Jiang

Prediction of optical spectra of complex solids remains a great challenge for first-principles calculation due to the huge computational cost of the state-of-the-art many-body perturbation theory based GW-Bethe Salpeter equation...

2017 ◽  
Author(s):  
Lyudmyla Adamska ◽  
Sridhar Sadasivam ◽  
Jonathan J. Foley ◽  
Pierre Darancet ◽  
Sahar Sharifzadeh

Two-dimensional boron is promising as a tunable monolayer metal for nano-optoelectronics. We study the optoelectronic properties of two likely allotropes of two-dimensional boron using first-principles density functional theory and many-body perturbation theory. We find that both systems are anisotropic metals, with strong energy- and thickness-dependent optical transparency and a weak (<1%) absorbance in the visible range. Additionally, using state-of-the-art methods for the description of the electron-phonon and electron-electron interactions, we show that the electrical conductivity is limited by electron-phonon interactions. Our results indicate that both structures are suitable as a transparent electrode.


2017 ◽  
Author(s):  
Lyudmyla Adamska ◽  
Sridhar Sadasivam ◽  
Jonathan J. Foley ◽  
Pierre Darancet ◽  
Sahar Sharifzadeh

Two-dimensional boron is promising as a tunable monolayer metal for nano-optoelectronics. We study the optoelectronic properties of two likely allotropes of two-dimensional boron using first-principles density functional theory and many-body perturbation theory. We find that both systems are anisotropic metals, with strong energy- and thickness-dependent optical transparency and a weak (<1%) absorbance in the visible range. Additionally, using state-of-the-art methods for the description of the electron-phonon and electron-electron interactions, we show that the electrical conductivity is limited by electron-phonon interactions. Our results indicate that both structures are suitable as a transparent electrode.


2019 ◽  
Vol 966 ◽  
pp. 489-493
Author(s):  
Desy Nicola Asturo ◽  
Ahmad Syahroni ◽  
Muhammad Aziz Majidi

Bi2Se3 has recently become the focus of research development due to its unique transport properties. It is a narrow band gap semiconductor with conducting states on its surface. A reliable and accurate calculation of the optical spectra including excitonic effects is very limited for this material. One of the reasons is that such calculations are computationally demanding since they require a very dense k-point sampling of the Brillouin zone. In this work, we use density functional theory as implemented in Quantum Espresso package to calculate the ground state properties of this material. Optical spectra are calculated within many-body perturbation theory by solving the Bethe-Salpeter equation in Yambo code to account for electron-hole interaction. A double-grid method implemented in Yambo helps us to do accurate calculations of the optical spectra with inexpensive computational cost. Furthermore, we expect that in bulk semiconductor with a narrow gap, electron-electron interaction is weak due to environmental screening. For this reason, to reduce the computational efforts, in this work we neglect the electron-electron interaction.


2005 ◽  
Vol 94 (18) ◽  
Author(s):  
Fabien Bruneval ◽  
Francesco Sottile ◽  
Valerio Olevano ◽  
Rodolfo Del Sole ◽  
Lucia Reining

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2091 ◽  
Author(s):  
Tie Yang ◽  
Liyu Hao ◽  
Rabah Khenata ◽  
Xiaotian Wang

In this work, we systematically studied the structural, electronic, magnetic, mechanical and thermodynamic properties of the fully compensated spin-gapless inverse Heusler Ti2MnAl compound under pressure strain condition by applying the first-principles calculation based on density functional theory and the quasi-harmonic Debye model. The obtained structural, electronic and magnetic behaviors without pressure are well consistent with previous studies. It is found that the spin-gapless characteristic is destroyed at 20 GPa and then restored with further increase in pressure. While, the fully compensated ferromagnetism shows a better resistance against the pressure up to 30 GPa and then becomes to non-magnetism at higher pressure. Tetragonal distortion has also been investigated and it is found the spin-gapless property is only destroyed when c/a is less than 1 at 95% volume. Three independent elastic constants and various moduli have been calculated and they all show increasing tendency with pressure increase. Additionally, the pressure effects on the thermodynamic properties under different temperature have been studied, including the normalized volume, thermal expansion coefficient, heat capacity at constant volume, Grüneisen constant and Debye temperature. Overall, this theoretical study presents a detailed analysis of the physical properties’ variation under strain condition from different aspects on Ti2MnAl and, thus, can provide a helpful reference for the future work and even inspire some new studies and lead to some insight on the application of this material.


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