scholarly journals Valance Band Maximum and Thermoelectric Properties of Bi\(_2\)O\(_2\)Se: First-Principles Calculations

2020 ◽  
Vol 30 (3) ◽  
Author(s):  
Van Quang Tran
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Band Structure ◽  
First Principles ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Transport Coefficients ◽  
Boltzmann Transport ◽  
Electronic Band ◽  
Band Maximum

Bi2O2Se has been known as a promising thermoelectric material with low thermal conductivity. Detail understanding of band structure is therefore important. In this report, by employing first-principles density functional theory and using primitive unit cell, the electronic band structure of Bi2O2Se is examined. The compound is found to be a narrow band gap semiconductor with very flat bands at the valence band maximum (VBM). Nevertheless, the curvature of energy surface at VBM is directional dependent. Overall, the heavy bands at VBM do not reduce drastically electrical conductivity. It is demonstrated by utilizing the solution of Boltzmann Transport Equation to compute the transport coefficients, i.e. the Seebeck coefficient, the electrical conductivity thereby the power factor and the electronic thermal conductivity. The figure of merit of the compound is also estimated and discussed. The p-type doping is suggested increasing the thermoelectric performance of the compound. All results are in good agreement with experiments and calculations reported earlier.

FIRST-PRINCIPLES STUDIES ON THE ELECTRONIC STRUCTURE OF LuPd2Si2

2009 ◽  
Vol 23 (32) ◽  
pp. 5929-5934 ◽  
Author(s):  
T. JEONG
Keyword(s):  
Band Structure ◽  
First Principles ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Local Density ◽  
Spin Orbit Coupling ◽  
Electronic Band ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Structure Scheme

The electronic band structure of LuPd 2 Si 2 was studied based on the density functional theory within local density approximation and fully relativistic schemes. The Lu 4f states are completely filled and have flat bands around -5.0 eV. The fully relativistic band structure scheme shows that spin–orbit coupling splits the 4f states into two manifolds, the 4f7/2 and the 4f5/2 multiplet.

scholarly journals DFT Study on the Carrier Concentration and Temperature-Dependent Thermoelectric Properties of Antimony Selenide

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Aditya Jayaraman ◽  
Abhijit Bhat Kademane ◽  
Muralikrishna Molli
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Thermoelectric Properties ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Hole Concentration ◽  
Electronic Band ◽  
Electronic Thermal Conductivity ◽  
Increasing Temperature ◽  
Antimony Selenide

We present the thermoelectric properties of Antimony Selenide (Sb2Se3) obtained using first principles calculations. We investigated the electronic band structure using the FP-LAPW method within the sphere of the density functional theory. Thermoelectric properties were calculated using BoltzTrap code using the constant relaxation time (τ) approximation at three different temperatures 300 K, 600 K, and 800 K. Seebeck coefficient (S) was found to decrease with increasing temperature, electrical conductivity (σ/τ) was almost constant in the entire temperature range, and electronic thermal conductivity (κ/τ) increased with increasing temperature. With increase in temperature S decreased from 1870 μV/K (at 300 K) to 719 μV/K (at 800 K), electronic thermal conductivity increased from 1.56 × 1015 W/m K s (at 300 K) to 3.92 × 1015 W/m K s (at 800 K), and electrical conductivity decreased from 22 × 1019/Ω m s (at 300 K) to 20 × 1019/Ω m s (at 800 K). The thermoelectric properties were also calculated for different hole concentrations and the optimum concentration for a good thermoelectric performance over a large range of temperatures (from 300 K to 1000 K) was found for hole concentration around 1019 cm−3.

Ab initio calculation on the Optical Properties of AA- Stacked two dimensional Graphene, Silicene, Germanene, and Stanene

2018 ◽  
Vol 1 (1) ◽  
pp. 46-50
Author(s):  
Rita John ◽  
Benita Merlin
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Complex Refractive Index ◽  
Single Layer ◽  
Generalized Gradient ◽  
Electronic Band ◽  
Wide Range ◽  
Optical Region

In this study, we have analyzed the electronic band structure and optical properties of AA-stacked bilayer graphene and its 2D analogues and compared the results with single layers. The calculations have been done using Density Functional Theory with Generalized Gradient Approximation as exchange correlation potential as in CASTEP. The study on electronic band structure shows the splitting of valence and conduction bands. A band gap of 0.342eV in graphene and an infinitesimally small gap in other 2D materials are generated. Similar to a single layer, AA-stacked bilayer materials also exhibit excellent optical properties throughout the optical region from infrared to ultraviolet. Optical properties are studied along both parallel (||) and perpendicular ( ) polarization directions. The complex dielectric function (ε) and the complex refractive index (N) are calculated. The calculated values of ε and N enable us to analyze optical absorption, reflectivity, conductivity, and the electron loss function. Inferences from the study of optical properties are presented. In general the optical properties are found to be enhanced compared to its corresponding single layer. The further study brings out greater inferences towards their direct application in the optical industry through a wide range of the optical spectrum.

FIRST PRINCIPLE CALCULATION OF ELECTRONIC BAND STRUCTURE AND OPTICAL PROPERTIES OF KIO3

2009 ◽  
Vol 23 (10) ◽  
pp. 2405-2412
Author(s):  
HARUN AKKUS ◽  
BAHATTIN ERDINC
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Electronic Band ◽  
Principle Calculation ◽  
First Principle Calculation ◽  
Functional Methods ◽  
A Value ◽  
Direct Band

The electronic band structure and optical properties of the ferroelectric single crystal KIO 3 have been investigated using the density functional methods. The calculated band structure for KIO 3 evidences that the crystal has a direct band gap with a value of 2.83 eV. The structural optimization has been performed. The real and imaginary parts of dielectric function, energy-loss function for volume and surface, and refractive index are calculated along the crystallographic axes.

First-principles studies of the elastic and magnetic properties of monolayer CrN

2021 ◽  
Author(s):  
Tai Ma ◽  
Jia Wang ◽  
Xu Li ◽  
Min Pu
Keyword(s):  
Magnetic Properties ◽  
Band Structure ◽  
First Principles ◽  
Electronic Band Structure ◽  
Strain Analysis ◽  
Exchange Interactions ◽  
Potential Method ◽  
Graphene Monolayer ◽  
Electronic Band ◽  
Spin Electronics

Two-dimensional (2D) materials with robust ferromagnetism properties have high potentials for application in the field of spintronics. However, extensively pursued 2D sheets, including pure graphene, monolayer BN, and layered transition metal dichalcogenides, are either nonmagnetic or weakly magnetic. The elastic, electronic and magnetic properties of monolayer CrN are calculated using the plane wave pseudo potential method based on first-principles density function theory. Upon determining through calculation that the structure of the monolayer CrN nanosheet is stable, its layer modulus [Formula: see text] shows that its strain resistance is stronger than that of graphene. Through strain analysis, materials with a monolayer CrN type of structure can be obtained. It is determined that 10% of the change in equilibrium area is still applicable to the 2D EOS, showing that this structure is quite stable. The spin-polarized electronic band structure is also calculated under different plane symmetry strains. The plane strain can be used to effectively adjust the metallic and magnetic properties of the material. Analyses of the band structure and density of states reveal that this material is half-metallic, where the origin of the ferromagnetism is related to [Formula: see text]–[Formula: see text] exchange interactions between the Cr and N atoms. Monolayer CrN has semimetallic properties and strong ferromagnetic (FM) properties. The FM effect can enhance the stability of the material. The results show that monolayer CrN is a semimetallic material with good elastic properties and a strong FM property. This material is therefore expected to have good application rospects in the field of spin electronics.

Computational Analysis of Strain Effects on Electrical Transport Properties of Crystalline Nanocomposite Thin Films

2011 ◽  
Author(s):  
Hua Li ◽  
Gang Li
Keyword(s):  
Thin Films ◽  
Electrical Conductivity ◽  
Band Structure ◽  
Transport Properties ◽  
Electrical Transport ◽  
Electronic Band Structure ◽  
Electrical Transport Properties ◽  
Electronic Band ◽  
Strain Effects ◽  
Nanocomposite Thin Films

In this work, we model the strain effects on the electrical transport properties of Si/Ge nanocomposite thin films. We utilize a two-band k·p theory to calculate the variation of the electronic band structure as a function of externally applied strains. By using the modified electronic band structure, electrical conductivity of the Si/Ge nanocomposites is calculated through a self-consistent electron transport analysis, where a nonequilibrium Green’s function (NEGF) is coupled with the Poisson equation. The results show that both the tensile uniaxial and biaxial strains increase the electrical conductivity of Si/Ge nanocomposite. The effects are more evident in the biaxial strain cases.

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