Topological phase and thermoelectric properties of bialkali bismuthide compounds (Na,K)2RbBi from first-principles

2021 ◽  
Author(s):  
Shahram Yalameha ◽  
Zahra Nourbakhsh ◽  
Daryoosh Vashaee
Keyword(s):  
Density Functional ◽  
Transport Coefficients ◽  
Relaxation Times ◽  
Surface States ◽  
Topological Phase ◽  
Boltzmann Transport ◽  
Thermoelectric Power Factor ◽  
Practical Applications ◽  
Wide Range ◽  
P Type

Abstract We report the topological phase, thermal, and electrical properties of bialkali bismuthide compounds (Na,K)2RbBi, as yet hypothetical. The topological phase transitions of these compounds under hydrostatic pressure are investigated. The calculated topological surface states and Z2 topological index confirm the nontrivial topological phase. The electronic properties and transport coefficients are obtained using the density functional theory combined with the Boltzmann transport equation. The relaxation times are determined using the deformation potential theory to calculate the electronic thermal and electrical conductivity. The calculated mode Grüneisen parameters are substantial, indicating strong anharmonic acoustic phonons scattering, which results in an exceptionally low lattice thermal conductivity. These compounds also have a favorable thermoelectric power factor leading to a relatively flat p-type figure-of-merit over a broad temperature range. Furthermore, the mechanical properties and phonon band dispersions show that these structures are mechanically and dynamically stable. Therefore, they offer excellent candidates for practical applications over a wide range of temperatures.

scholarly journals Band degeneracy enhanced thermoelectric performance in layered oxyselenides by first-principles calculations

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Ning Wang ◽  
Menglu Li ◽  
Haiyan Xiao ◽  
Zhibin Gao ◽  
Zijiang Liu ◽  
...  
Keyword(s):  
Density Functional ◽  
Transport Theory ◽  
Relaxation Times ◽  
Wide Band ◽  
Type Systems ◽  
Model Systems ◽  
Boltzmann Transport ◽  
Seebeck Coefficients ◽  
Boltzmann Transport Theory ◽  
P Type

AbstractBand degeneracy is effective in optimizing the power factors of thermoelectric (TE) materials by enhancing the Seebeck coefficients. In this study, we demonstrate this effect in model systems of layered oxyselenide family by the density functional theory (DFT) combined with semi-classical Boltzmann transport theory. TE transport performance of layered LaCuOSe and BiCuOSe are fully compared. The results show that due to the larger electrical conductivities caused by longer electron relaxation times, the n-type systems show better TE performance than p-type systems for both LaCuOSe and BiCuOSe. Besides, the conduction band degeneracy of LaCuOSe leads to a larger Seebeck coefficient and a higher optimal carrier concentration than n-type BiCuOSe, and thus a higher power factor. The optimal figure of merit (ZT) value of 1.46 for n-type LaCuOSe is 22% larger than that of 1.2 for n-type BiCuOSe. This study highlights the potential of wide band gap material LaCuOSe for highly efficient TE applications, and demonstrates that inducing band degeneracy by cations substitution is an effective way to enhance the TE performance of layered oxyselenides.

Interfacial defect engineering and Photocatalysis Properties of hBN/MX2(M = Mo, W, and X = S, Se) Heterostructures

2021 ◽  
Author(s):  
Zhihai Sun ◽  
Jiaxi Liu ◽  
Ying Zhang ◽  
Ziyuan Li ◽  
Leyu Peng ◽  
...  
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Band Alignment ◽  
Type I ◽  
Defect Engineering ◽  
Wide Range ◽  
Interfacial Defects ◽  
Significant Research ◽  
P Type ◽  
The Impact

Abstract Van der Waals (VDW) heterostructures have attracted significant research interest due to their tunable interfacial properties and potential in a wide range of applications such as electronics, optoelectronic, and heterocatalysis. In this work, the impact of interfacial defects on the electronic structures and photocatalytic properties of hBN/MX2(M = Mo, W, and X = S, Se) are studied using density functional theory calculations. The results reveal that the band alignment of hBN/MX2 can be adjusted by introducing vacancies and atomic doping. The type-I band alignment of the host structure was maintained in the heterostructure with n-type doping in the hBN sublayer. Interestingly, the band alignment changed to the type-II heterostructrue as VB defect and p-type doping was introduced in the hBN sublayer. This could be profitable for the separation of photo-generated electron−hole pairs at the interfaces and is highly desired for heterostructure photocatalysis. In addition, two Z-type heterostructures including hBN(BeB)/MoS2, hBN(BeB)/MoSe2, and hBN(VN)/MoSe2 were achieved, showing reducing band gap and ideal redox potential for water splitting. Our results reveal the possibility of engineering the interfacial and photocatalysis properties of hBN/MX2 heterostructures via interfacial defects.

Ab-initio study of mechanical and thermoelectric properties of topological semimetal: LaAuPb

2021 ◽  
Author(s):  
Megha Goyal ◽  
M.M. Sinha
Keyword(s):  
Thermoelectric Properties ◽  
Density Functional ◽  
Transport Theory ◽  
Poisson Ratio ◽  
Topological Phase ◽  
Boltzmann Transport ◽  
Functional Theory ◽  
Boltzmann Transport Theory ◽  
Material Fabrication ◽  
The Stability

Abstract Heusler compounds are a tuneable class of material with a cubic crystal structure that can serve as a platform to study the topological phase of a material. These materials have numerous technological and scientific applications. So, in the present work, the mechanical, thermodynamical, and thermoelectric properties of LaAuPb in the topological phase have been reported by using density functional theory and Boltzmann transport theory. LaAuPb is mechanically stable, and the Poisson ratio reveals its ductile nature. The specific heat of the proposed compound at room temperature is 73.94 J K-1 mol-1 at constant volume. Debye’s temperature is estimated to be 188.64K. Moreover, the lattice thermal conductivity of the compound is 14.64 W/mK and 3.66 W/mK at 300K and 1200K, respectively. Good thermoelectric response of LaAuPb can be confirmed by its high value of the figure of merit (0.46) at 1200K. Hence, it is a potential material for thermoelectric applications. This work will help future researchers to better understand the stability, nature and behaviour of LaAuPb in material fabrication.

A High Thermoelectric Performance ZT in p-Type LaSe2 Crystal

2021 ◽  
Vol 871 ◽  
pp. 203-207
Author(s):  
Jian Liu
Keyword(s):  
Thermal Conductivity ◽  
Power Factor ◽  
High Power ◽  
Density Functional ◽  
Lattice Thermal Conductivity ◽  
Phonon Transport ◽  
Thermoelectric Performance ◽  
Boltzmann Transport ◽  
High Power Factor ◽  
P Type

In this work, we use first principles DFT calculations, anharmonic phonon scatter theory and Boltzmann transport method, to predict a comprehensive study on the thermoelectric properties as electronic and phonon transport of layered LaSe2 crystal. The flat-and-dispersive type band structure of LaSe2 crystal offers a high power factor. In the other hand, low lattice thermal conductivity is revealed in LaSe2 semiconductor, combined with its high power factor, the LaSe2 crystal is considered a promising thermoelectric material. It is demonstrated that p-type LaSe2 could be optimized to exhibit outstanding thermoelectric performance with a maximum ZT value of 1.41 at 1100K. Explored by density functional theory calculations, the high ZT value is due to its high Seebeck coefficient S, high electrical conductivity, and low lattice thermal conductivity .

The n- and p-type thermoelectric response of a semiconducting Co-based quaternary Heusler alloy: a density functional approach

2019 ◽  
Vol 7 (25) ◽  
pp. 7664-7671 ◽  
Author(s):  
Enamullah Enamullah ◽  
Pil-Ryung Cha
Keyword(s):  
Electronic Structure ◽  
Thermoelectric Properties ◽  
Heusler Alloy ◽  
Density Functional ◽  
Transport Theory ◽  
Mechanical Stability ◽  
Functional Approach ◽  
Boltzmann Transport ◽  
Boltzmann Transport Theory ◽  
P Type

In the combined framework of density functional and Boltzmann transport theory, we have systematically studied the electronic structure, mechanical stability and thermoelectric properties of the semiconducting quaternary Heusler alloy, CoFeTiAl.

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.

Persistent Photocurrent in InP Nanowires Heteroepitaxially Bridged Between Single Crystal Si Surfaces

2008 ◽  
Vol 1080 ◽  
Author(s):  
Ataur Sarkar ◽  
M. Saif Islam ◽  
Sungsoo Yi ◽  
A. Alec Talin
Keyword(s):  
Single Crystal ◽  
Room Temperature ◽  
Relaxation Times ◽  
Single Crystal Silicon ◽  
Surface States ◽  
Photonic Devices ◽  
Crystal Silicon ◽  
Slow Decay ◽  
Visible Laser ◽  
P Type

ABSTRACTRoom temperature photoelectrical characterization with 325-nm ultraviolet and 633-nm visible laser excitations is performed on lateral p-type InP nanowires bridged between vertically oriented heavily p-doped single crystal silicon electrodes. Experimental results under 5 V bias demonstrate persistent photoconductivity through a slow decay of excess photocurrent with relaxation times ∼110 s and ∼50 s for the UV and visible laser illuminations, respectively. Persistent photocurrent originates from the long recombination time due to carrier trapping in vacancies, defect centers, and surface states in the InP nanowires. The study opens a new understanding of trap physics of nanowire heterostructures, a critical investigation for applications of these materials in photonic devices.

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.

scholarly journals Optimal Carrier Concentration for High Thermoelectric Performance of Lead Substituted Bismuth Telluride in p-Type Doping

2018 ◽  
Vol 28 (2) ◽  
pp. 169
Author(s):  
Van Quang Tran
Keyword(s):  
Carrier Concentration ◽  
Thermoelectric Materials ◽  
Density Functional ◽  
Room Temperature ◽  
Density Functional Theory Calculation ◽  
Binary Compound ◽  
Thermoelectric Performance ◽  
Boltzmann Transport ◽  
Relaxation Time Approximation ◽  
P Type

Bi\(_{2}\)Te\(_{3}\) and its alloys are the well-known state-of-the-art thermoelectric materials operating at around room temperature. With lead substituted, the newly formed quasi-binary compound PbBi\(_{4}\)Te\(_{7}\), shows relatively high electrical conductivity and Seebeck coefficient. In this report, we employed the solution of the Boltzmann Transport Equation in a constant relaxation-time approximation within a first-principles density-functional-theory calculation to explore the role of the electronic thermal conductivity, \(\kappa _{e}\), on the thermoelectric performance of the compound with p-type doping. Results show that \(\kappa _{e}\) increases drastically with the increases of both temperature and carrier concentration. Even the power factor has been found to be markedly improved with the increase of the carrier concentration, a rapid increase of \(\kappa _{e}\) emerges as a big hindrance to improve the dimensionless figure of merit, ZT, of the compound. This is responsible for the limit of ZT. The larger ZT is found in low temperatures and carrier concentrations. The highest ZT of about 0.48 occurs at 223 K and at the carrier concentration of \(6\times 10^{17}\)cm\(^{ - 3}\). At room temperature the maximum ZT is slightly smaller. We demonstrated that at a particular temperature to maximize the thermoelectric performance of the compound, the carrier concentration must be optimized. Results show that the compound with p-type doping is a promising thermoelectric materials operating at around room temperature.

Thermoelectric power factor enhancement in metal/semiconductor nanocomposites by ionized nanoparticle scattering

2011 ◽  
Vol 1329 ◽  
Author(s):  
Je-Hyeong Bahk ◽  
Zhixi Bian ◽  
Mona Zebarjadi ◽  
Parthi Santhanam ◽  
Rajeev Ram ◽  
...  
Keyword(s):  
Thermoelectric Power ◽  
Power Factor ◽  
Coulomb Potential ◽  
Metallic Nanoparticles ◽  
Transport Coefficients ◽  
Finite Size ◽  
Boltzmann Transport ◽  
Thermoelectric Power Factor ◽  
The Matrix ◽  
Semiconductor Nanocomposites

ABSTRACTWe present a theoretical investigation of the thermoelectric power factor enhancement in metal/semiconductor nanocomposites by the energy dependent electron scattering from ionized nanoparticles. The metal nanoparticles embedded in semiconductors can be ionized to donate electrons to the matrix, which will result in a Coulomb potential tail around the nanoparticles. Here we show the significant effect of slowly varying potential tails on thermoelectric properties of the nanocomposites. The Coulomb potential is different from that of the conventional ionized impurities due to the finite size of the ionized particles, and the fact that the nanoparticles can give multiple electrons to the matrix. Detailed calculations for scattering rates and thermoelectric coefficients are presented for ErAs semi-metallic nanoparticles in InGaAs semiconductors. The partial wave method is used to consider the exact potential profile around nanoparticles and Boltzmann transport equation is used to calculate the transport coefficients. We find that an increase by 15~30% in power factor can be achieved over a wide temperature range in these material systems in addition to the thermal conductivity reduction to further enhance ZT.

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