scholarly journals Strain Effects on the Electronic and Thermoelectric Properties of n(PbTe)-m(Bi2Te3) System Compounds

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4086
Author(s):  
Weiliang Ma ◽  
Marie-Christine Record ◽  
Jing Tian ◽  
Pascal Boulet
Keyword(s):  
Density Functional ◽  
Lattice Thermal Conductivity ◽  
Compressive Strain ◽  
Van Der Waals Interactions ◽  
Functional Theory ◽  
Band Engineering ◽  
Seebeck Coefficients ◽  
The Density Functional Theory ◽  
P Type ◽  
Narrow Band Gap Semiconductors

Owing to their low lattice thermal conductivity, many compounds of the n(PbTe)-m(Bi2Te3) homologous series have been reported in the literature with thermoelectric (TE) properties that still need improvement. For this purpose, in this work, we have implemented the band engineering approach by applying biaxial tensile and compressive strains using the density functional theory (DFT) on various compounds of this series, namely Bi2Te3, PbBi2Te4, PbBi4Te7 and Pb2Bi2Te5. All the fully relaxed Bi2Te3, PbBi2Te4, PbBi4Te7 and Pb2Bi2Te5 compounds are narrow band-gap semiconductors. When applying strains, a semiconductor-to-metal transition occurs for all the compounds. Within the range of open-gap, the electrical conductivity decreases as the compressive strain increases. We also found that compressive strains cause larger Seebeck coefficients than tensile ones, with the maximum Seebeck coefficient being located at −2%, −6%, −3% and 0% strain for p-type Bi2Te3, PbBi2Te4, PbBi4Te7 and Pb2Bi2Te5, respectively. The use of the quantum theory of atoms in molecules (QTAIM) as a complementary tool has shown that the van der Waals interactions located between the structure slabs evolve with strains as well as the topological properties of Bi2Te3 and PbBi2Te4. This study shows that the TE performance of the n(PbTe)-m(Bi2Te3) compounds is modified under strains.

scholarly journals Effect of Nitrogen Cation as “Electron Trap” at π-Linker on Properties for p-Type Photosensitizers: DFT Study

Molecules ◽  
2019 ◽  
Vol 24 (17) ◽  
pp. 3134 ◽  
Author(s):  
Zhi-Dan Sun ◽  
Jiang-Shan Zhao ◽  
Xue-Hai Ju ◽  
Qi-Ying Xia
Keyword(s):  
Driving Force ◽  
Density Functional ◽  
Electron Trap ◽  
Hole Injection ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Td Dft ◽  
Harvesting Efficiency ◽  
Light Harvesting Efficiency ◽  
P Type

On the basis of thieno(3,2-b)thiophene and dithieno[3,2-b:2′,3′-d]thiophene (T2 and T3 moieties) as π-linker, the A, D and S series dyes were designed to investigate the effect of the introducing N+ as an “electron trap” into T2 and T3 on the properties of the dyes. The optimized structures, electronic and optical properties were investigated by the density functional theory (DFT) and time-dependent DFT (TD-DFT). The results show that the properties of the dyes are sensitive to the N+ position in π-linkers. D series dyes with electron-withdrawing units located near the donor have better properties than the corresponding A series with the electron-withdrawing units located near the acceptor. For A and D series, the N+ modified dye named T2N+1-d displays the largest red shift of the UV–vis absorption, the maximum integral values of the adsorption-wavelength curves over the visible light, the highest light harvesting efficiency (LHE, 0.996), and the strongest adsorption energy (−44.33 kcal/mol). T2N+1-d also has a large driving force of hole injection (ΔGinj, −0.74 eV), which results in a more efficient hole injection. Bearing a lengthier π-linker than T2N+1-d, the properties of T2N+1-s are further improved. T2N+1-d moiety or its increased conjugated derivatives may be a promising π-linker.

Thermoelectric performance of MoSi(2)As(4) monolayer

2022 ◽  
Author(s):  
Yuhong Huang ◽  
Xuanhong Zhong ◽  
Hongkuan Yuan ◽  
Hong Chen
Keyword(s):  
Figure Of Merit ◽  
Density Functional ◽  
Lattice Thermal Conductivity ◽  
Thermoelectric Performance ◽  
Potential Candidate ◽  
Boltzmann Transport ◽  
Maximal Power ◽  
Thermoelectric Figure ◽  
Functional Theory ◽  
P Type

Abstract Thermoelectric performance of MoSi2As4 monolayer is investigated using density functional theory combined with Boltzmann transport theoy. The maximal power factors of n- and p-type by PBE (HSE06) functional are 7.73 (48.31) and 32.84 (30.50) mW m-1 K-2 at the temperature of 1200 K, respectively. The lattice thermal conductivity is less than 30 W m-1 K-1 above 800 K. The thermoelectric figure of merit can reach 0.33 (0.58) and 0.90 (0.81) using PBE (HSE06) functional for n- and p-type under appropriate carrier concentration at 1200K, respectively. Thus, the p-type MoSi2As4 monolayer is predicted to be a potential candidate for high-temperature thermoelectric applications.

scholarly journals Prediction for electronic, vibrational and thermoelectric properties of chalcopyrite AgX(X=In,Ga)Te 2 : PBE + U approach

2017 ◽  
Vol 4 (10) ◽  
pp. 170750 ◽  
Author(s):  
Jianhui Yang ◽  
Qiang Fan ◽  
Xinlu Cheng
Keyword(s):  
Density Functional ◽  
Functional Results ◽  
Chalcopyrite Structure ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Thermoelectric Transport ◽  
The Density Functional Theory ◽  
Wide Range ◽  
Thermoelectric Transport Properties ◽  
P Type

The electronic, vibrational and thermoelectric transport characteristics of AgInTe 2 and AgGaTe 2 with chalcopyrite structure have been investigated. The electronic structures are calculated using the density-functional theory within the generalized gradient approximation (GGA) of Perdew–Burke–Ernzerhof functional considering the Hubbard-U exchange correlation. The band-gaps of AgInTe 2 and AgGaTe 2 are much larger than previous standard GGA functional results and agree well with the existing experimental data. The effective mass of the hole and the shape of density of states near the edge of the valence band indicate AgInTe 2 and AgGaTe 2 are considerable p-type thermoelectric materials. An analysis of lattice dynamics shows the low thermal conductivities of AgInTe 2 and AgGaTe 2 . The thermoelectric transport properties' dependence on carrier concentration for p-type AgInTe 2 and AgGaTe 2 in a wide range of temperatures has been studied in detail. The results show that p-type AgInTe 2 and AgGaTe 2 at 800 K can achieve the merit values of 0.91 and 1.38 at about 2.12 × 10 20  cm −3 and 1.97 × 10 20  cm −3 carrier concentrations, respectively. This indicates p-type AgGaTe 2 is a potential thermoelectric material at high temperature.

The mechanical, optical and thermoelectric properties of MCoF3 (M = K and Rb) compounds

2017 ◽  
Vol 31 (06) ◽  
pp. 1750033 ◽  
Author(s):  
A. A. Mubarak
Keyword(s):  
Thermoelectric Properties ◽  
Density Functional ◽  
Full Potential ◽  
Functional Theory ◽  
Half Metallic ◽  
Augmented Plane Wave ◽  
The Density Functional Theory ◽  
Type Character ◽  
P Type ◽  
Linearized Augmented Plane Wave

This is an ab initio study instituted on the density functional theory (DFT) and the full-potential linearized augmented plane wave (FP-LAPW) calculations that are performed to analyze the mechanical, electronic, optical and thermoelectric properties of the cubic MCoF3 compound (M = K and Rb). The studied compounds are found thermodynamically and mechanically stable. Moreover, these compounds are found to be elastically anisotropic and ductile. KCoF3 and RbCoF3 are classified as half-metallic and anti-ferromagnetic compounds. The optical properties are investigated from the dielectric function for the different energy ranges. The thermoelectric properties such as transport properties are determined as a function of temperature using BoltzTrape code in the range of 20–800 K. The present compounds are found to have p-type character. Also, the majority charge carriers are found to be electrons rather than hole. Useful mechanical, spintronic, optical and thermoelectric applications are predicted based upon the calculations.

scholarly journals Влияние размерных эффектов на электронную структуру гексагонального теллурида галлия

2018 ◽  
Vol 60 (9) ◽  
pp. 1645
Author(s):  
А.В. Кособуцкий ◽  
С.Ю. Саркисов
Keyword(s):  
Density Functional ◽  
Electronic Band Structure ◽  
Bulk Material ◽  
Structural Parameters ◽  
Van Der Waals Interactions ◽  
Electronic Band ◽  
Functional Theory ◽  
Lower Conduction Band ◽  
The Density Functional Theory ◽  
Indirect Band Gap

AbstractUsing methods of the density functional theory, the electronic band structure of a hexagonal modification of the layered GaTe semiconductor has been calculated. The structural parameters of a bulk crystal with the β-polytype symmetry have been determined taking into account van der Waals interactions and agree with experimental data for polycrystalline films within 2%. Estimates for the position of extrema of the upper valence band and the lower conduction band have been obtained with respect to the vacuum level for bulk β-GaTe and for ultrathin plates with the number of elementary layers ranging from 1 to 10, which corresponds to a thickness range of 0.5–8 nm. The calculations demonstrate that hexagonal GaTe is an indirect band gap semiconductor with a forbidden band width varying from 0.8 eV in the bulk material to 2.3 eV in the monolayer.

F2 storage by confinement inside carbon nanotubes

2016 ◽  
Vol 94 (1) ◽  
pp. 15-19 ◽  
Author(s):  
Wiem Felah Gtari ◽  
Bahoueddine Tangour
Keyword(s):  
Carbon Nanotubes ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Density Functional Theory Method ◽  
Van Der Waals Interactions ◽  
Basis Set ◽  
Basis Sets ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Walled Carbon Nanotubes

Theoretical calculations have been achieved to study the interaction between the confined F2 molecule along the nanotube axis and perpendicular to it and armchair (n,n) single-walled carbon nanotubes with n = 4, 5, 6, 7, and 8 and the zig-ag nanotube (9,0) using the density functional theory method with the CAM-B3LYP functional and both cc-pVQZ and STO-3G basis sets. The interaction of the F2 molecule with the nanotube is different according to the molecular orientation, the chirality of the carbon nanotube, and the confinement space extension. These results interpreted by means of van der Waals interactions reveal anisotropic and competitive behavior at the nanometric level. The π electrons of the nanotube interact with the lone pairs of F2 highlighting its lateral polarizability. The encapsulated F2 molecule is stable along and perpendicular to the nanotube (5,5) and (6,6) axis. The best stabilization energy is obtained fornanotube (5,5) at the perpendicular position using the cc-pVQZ basis set.

LARGE HOLE POLARONS IN Sc-DOPED TiO2 CRYSTALS

2013 ◽  
Vol 27 (15) ◽  
pp. 1350113 ◽  
Author(s):  
ARVIDS STASHANS ◽  
YESSICA BRAVO
Keyword(s):  
Density Functional ◽  
Local Defect ◽  
Large Radius ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Large Hole ◽  
The Density Functional Theory ◽  
Doped Titania ◽  
P Type

First-principles calculations based on the density functional theory (DFT) within the generalized gradient approximation (GGA) have been used to study Sc -doped TiO 2, rutile and anatase, crystals. Local defect microstructure, electronic and electrical properties have been obtained and discussed in the present work. Large radius hole polaron state found here points out to the possibility of p-type electrical conductivity in Sc -doped titania.

First-principles study of intrinsic defects in CdO

2018 ◽  
Vol 32 (06) ◽  
pp. 1850059 ◽  
Author(s):  
V. P. Zhukov ◽  
N. I. Medvedeva ◽  
V. N. Krasilnikov
Keyword(s):  
Density Functional ◽  
Oxygen Vacancies ◽  
Cadmium Oxide ◽  
Metallic Phase ◽  
Hydrogen Atmosphere ◽  
Free Energies ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Metallic Cadmium ◽  
P Type

Using the density functional theory (DFT) in the GGA and LSDA + U approximations, we studied the effect of cadmium atoms in the interstitial sites and vacancies in the oxygen and cadmium sublattices on the electronic structure of rock-salt cadmium oxide (CdO). Migration of cadmium atoms into interstitial sites was shown to be unlikely. In the presence of oxygen vacancies, the behavior of CdO remains semiconducting and nonmagnetic. Cadmium vacancies induce d0 ferromagnetism and spin-dependent conductivity, which is semiconducting for spin-up electrons and is p-type metallic for spin-down electrons. The formation energies and free energies were calculated for oxygen vacancies and metallic cadmium phase, which allowed an explanation to be offered for the large number of vacancies and the metallic phase formed during reduction in hydrogen atmosphere.

scholarly journals Electronic and Thermoelectric Properties in Li-Based Half-Heusler Compounds: A First Principle Study

2019 ◽  
Vol 61 (1) ◽  
pp. 44-55
Author(s):  
Y. Benazouzi ◽  
H. Rozale ◽  
M. A. Boukli Hacene ◽  
M. Khethir ◽  
A. Chahed ◽  
...  
Keyword(s):  
Thermoelectric Properties ◽  
Density Functional ◽  
First Principle ◽  
Generalized Gradient ◽  
Functional Theory ◽  
High Power Factor ◽  
The Density Functional Theory ◽  
Direct Band ◽  
Frame Work ◽  
P Type

AbstractIn this paper, we performed a first principle study for new half-Heusler LiSrX(X= N, P, and As) working with WIEN2k code in the frame work of the density functional theory, and the Boltzmann theory. We estimated the exchange-correlation potential by the generalized gradient approximation (GGA). Energetically, the three compounds show a high stability in structure type2, we notice that the lattice constant increased while bulk modulus decreased in replacing the ions of size increasing. Based on our calculations, LiSrN, LiSrP, and LiSrAs compounds are mechanically stable, and show semiconductor nature with indirect band gaps of 1.21, 1.75 for LiSrN and LiSrAs, and direct band gap of 1.94 eV for LiSrP. The thermoelectric properties are calculated for LiSrX (X=N, P, and As) and they found a high power factor for the p-type doping concentration.

First-Principles Study on Ga-N Co-Doped P-Type ZnO

2011 ◽  
Vol 299-300 ◽  
pp. 498-502 ◽  
Author(s):  
Hong Sheng Zhao ◽  
Yu Dan Gu ◽  
Nan Zhang ◽  
Ya Hong Gao
Keyword(s):  
Density Of States ◽  
Density Functional ◽  
Partial Density ◽  
Total Density ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Donor Acceptor ◽  
P Type ◽  
Total Density Of States ◽  
Co Doped

Based on the density functional theory, the structure of pure ZnO, N doped, and Ga-N/Ga-2N co-doped wurtzite ZnO was calculated by using first-principle plane wave ultrasoft pseudopotential method. Electronic structures of these ZnO-based doping syetems were studied. The calculations of band structure, total density of states, and partial density of states show that Ga-2N donor/acceptor co-doped ZnO is easier to implement the p-type ZnO than other cases.

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