Gui Yang, jueming Yang, Yuli Yan, Yuanxu Wang
The electronic structure and thermoelectric properties of are studied by the first principles and the semiclassical BoltzTrap theory.
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The unique structure of Zintl phase makes it an ideal system to realize the concept of phonon-glass and electron-crystal in the thermoelectric community. In this work, by combining first-principles calculations and Boltzmann transport theory for both electrons and phonons, we demonstrate that the ZT value of Zintl compound KSnSb can reach ~2.6 at 800 K. Such extraordinary thermoelectric performance originates from the large Seebeck coefficient due to multi-valley band structures and particularly very small lattice thermal conductivity caused by mixed-bond characteristics.
Ca$_{10}$GdCdSb$_9$ is a new Zintl phase with a large unit cell volume (~2500 Å3) and a very complex, disordered structure, which can drive the realization of ultralow thermal conductivity in this material. The measured Seebeck coefficient, $α$, for single-crystalline Ca$_{10}$GdCdSb$_9$ approaches 350 $μ$V/K at 600 K. The experimentally determined electrical resistivity of Ca$_{10}$GdCdSb$_9$ is very low, leading to a remarkably high-power factor PF of 23.2 $μ$W/cm.K$^2$ at 460 K. The extraordinary PF value in this material, higher than those of the currently known state-of-the-art materials …
Designing new Zintl phases SrBaX (X = Si, Ge, Sn) for thermoelectric applications using \textit{ab initio} techniques
本文通过第一性原理计算设计新型Zintl相SrBaX（X = Si, Ge, Sn），发现其具有极低晶格热导率和优异热电性能，其中SrBaGe在700 K时ZT约为2.0，且p型和n型掺杂性能相当，有望成为高性能热电材料。
We investigate the thermoelectric properties of CaAl$_2$Si$_2$-type Zintl phase compounds $AB_2X_2$ ($A$ = Mg, Ca, Sr, Ba, $B$ = Mg, Zn, Cd, and $X$ = P, As, Sb) using first principles band calculations within the Boltzmann transport theory assuming the constant relaxation time approximation. We introduce the effective degree of valley degeneracy $n_{TE}$ to focus on the relationship between the thermoelectric properties and the multivalley character of the electronic band structure around the Fermi level. We also introduce a quantity $γ_{TE}$, which takes into account $n_{TE}$ and anisotropy …
Intermetallic semiconductors with the cubic Half-Heusler structure (XYZ) have excellent thermoelectric properties. This has been attributed to the high degeneracy of the carrier pockets in the band structure, but large differences are found between different material compositions. Half-Heuslers are often interpreted within Zintl chemistry, making a clear distinction between an electropositive cation ($X^{n+}$) and an extended polyanion ($YZ^{n-}$). Based on quantitative real space chemical bonding analysis, we unravel large degrees of covalent bonding between the formal cation and anion, makin…
Promising High Temperature Thermoelectric Performance of Alkali Metal-based Zintl phases X$_2$AgY (X = Na, K; Y = Sb, Bi): Insights from First-Principles Studies
本研究利用第一性原理方法发现碱金属基Zintl相X$_2$AgY (X = Na, K; Y = Sb, Bi)因晶格非简谐性等具有极低晶格热导率，在700 K下展现出高达2.1的热电优值，为高性能热电材料设计提供了新方向。
We explore the topological behavior of the binary Zintl phase of the alkaline earth metals based compounds Sr$_2$Pb and Sr$_2$Sn using both standard and hybrid density functional theory. It is found that Sr$_2$Pb lies on the verge of a topological instability which can be suitably tuned through the application of a small uniaxial expansion strain ($>$ 3%). The resulting non-trivial topologically insulating state display well-defined metallic states in the Sr$_{2}$Pb(010) surface, whose evolution is studied as a function of the film thickness.
We introduce a simple but efficient electronic fitness function (EFF) that describes the electronic aspect of the thermoelectric performance. This EFF finds materials that overcome the inverse relationship between $σ$ and $S$ based on the complexity of the electronic structures regardless of specific origin (e.g., isosurface corrugation, valley degeneracy, heavy-light bands mixture, valley anisotropy or reduced dimensionality). This function is well suited for application in high throughput screening. We applied this function to 75 different thermoelectric and potential thermoelectric material…
Structural and elastic properties of Ba$_{2}$P$_{7}$X (X=Cl, Br, I) (Barium Phosphide Halides) Zintl compounds have been investigated using the pseudo-potential plane-wave (PP-PW) method based on the density functional theory (DFT) within the generalized gradient approximation (GGA-PBESOL). The calculated lattice constants and internal parameters are in a good agreement with the experimental results reported in literature. In this paper, we present an investigation of the relative changes of the structural parameters and elastic constants as function of hydrostatic pressure. Isotropic elastic …
High Thermoelectric Performance via Stacking-Controlled Symmetry Breaking in Layered XZnBi (X = Rb, Cs) Zintl Materials
通过第一性原理计算和玻尔兹曼方程，研究了层状Zintl化合物XZnBi (X=Rb, Cs)的堆叠顺序对热电性能的影响，发现其具有高能带简并度、布丁模能带和低热导率，在900 K下ZT值最高达2.42（CRTA）或0.52（含电声耦合）。
Alloying to Tune the Bandgap of the AM2Pn2 Zintl Compounds
本研究针对AM₂Pn₂ Zintl化合物的带隙调控需求，采用高通量第一性原理计算筛选合金，得到适用于叠层顶电池和远红外探测器的候选材料，并通过实验验证了该类合金的可合成性。
The bulk photovoltaic effect (BPVE) is a phenomenon which creates a net electrical current from sunlight in a polar noncentrosymmetric material possessing a moderate band gap. This effect is being explored as an alternative to traditional pn-junction solar cells to convert solar energy into electricity. This paper assesses the possibility that hydrogenated Zintl-phase compounds consisting only of metal, metalloid, and hydrogen atoms, may be able to provide a BPVE response. Towards this end, the magnitude of the BPVE shift current is calculated for each of the compounds AeTrTtH (Ae = Ca, Sr, an…
Motivated by a recent theoretical suggestion that doping electrons into various CaAl$_2$Si$_2$-type Zintl phase compounds may give rise to high thermoelectric performance, we explore the possibility of n-type (electron carrier) doping of CaZn$_2X_2$ ($X$ = As, P) using first principles calculation. We consider n-type doping of CaZn$_2X_2$ with the following two situations: interstitial-site doping of alkaline earth metals $AE$ (= Mg, Ca, Sr, Ba) and group 3 elements $G3$ (= Sc, Y, La), and $G3$ substitutional doping for the Ca site. The evaluation of the formation energy of these defects in va…
Pressure-induced Superconductivity and Structure Phase Transition in SnAs-based Zintl Compound SrSn2As2
本文系统研究了高压下Zintl化合物SrSn2As2的晶体结构与电子性质，发现其在约20.8 GPa时发生三方到单斜的结构相变并诱导出超导性，揭示了层状SnAs基化合物在压缩下的新基态。
A Map of the Zintl AM2Pn2 Compounds: Influence of Chemistry on Stability and Electronic Structure
本文基于第一性原理研究了AM2Pn2 Zintl相的基态结构、热力学稳定性和电子结构，发现其带隙覆盖0至3 eV以上，提出了多种太阳能吸收器和红外探测器候选材料，并指出Mg3Sb2因独特的价带口袋成为最具潜力的热电材料。
Ab initio study of NaSrSb and NaBaSb as potential thermoelectric prospects
本研究采用第一性原理结合玻尔兹曼输运理论，探究NaSrSb和NaBaSb两种Zintl相的热电性能，发现其晶格热导率低，n型下热电优值较高，为后续实验研究提供了理论基础。
In search of better thermoelectric materials, we have systematically investigated the thermoelectric properties of a 122 Zintl phase compound EuCd$_{2}$As$_{2}$ using \textit{ab-initio} density functional theory and semi-classical Boltzmann transport theory within constant relaxation time approximation. Considering the ground state magnetic structure which is A-type antiferromagnetic (A-AFM) and non-magnetic (NM) structure, we evaluated various thermoelectric parameters such as Seebeck coefficient, electrical and thermal conductivity, power factor and figure of merit (ZT) as function temperatu…
The experimental search for new thermoelectric materials remains largely confined to a limited set of successful chemical and structural families, such as chalcogenides, skutterudites, and Zintl phases. In principle, computational tools such as density functional theory (DFT) offer the possibility of rationally guiding experimental synthesis efforts toward very different chemistries. However, in practice, predicting thermoelectric properties from first principles remains a challenging endeavor, and experimental researchers generally do not directly use computation to drive their own synthesis …
Evidence of variable range hopping in the Zintl phase EuIn2P2
本研究全面表征Zintl相单晶EuIn₂P₂的多类物理性质，证实其磁有序特征，发现40K以上电输运由短程磁相互作用主导且符合变程跳跃模型，负磁阻的二次方依赖及拉曼光谱结果进一步佐证该机制。
Stark difference in the in-plane anomalous Hall response in Zintl compounds EuA2Sb2 (A = Zn, Cd) thin films
该研究对比EuZn2Sb2与EuCd2Sb2薄膜的面内反常霍尔效应，揭示其符号和磁场依赖的显著差异，并归因于不同的能带反转参数。
The discovery of high thermoelectric performance in n-type polycrystalline Mg3(Sb,Bi)2 based Zintl compounds has ignited intensive research interest. However, some fundamental questions concerning the anisotropic transport properties and the origin of intrinsically low thermal conductivity are still elusive, requiring the investigation of single crystals. In this work, high-quality p-type Mg3Sb2 and Mg3Bi2 single crystals have been grown by using a self-flux method. The electrical resistivity \r{ho} of Mg3Bi2 single crystal displays an anisotropy with \r{ho} in-plane twice larger than out-of-p…
Hybrid-order topology in unconventional magnets of Eu-based Zintl compounds with surface-dependent quantum geometry
本研究预测Eu基Zintl化合物具有混合阶拓扑，产生表面依赖的量子几何，并可在磁场下转变为理想Weyl半金属，为拓扑输运和超导提供新平台。
Experimental results have shown that the quaternary compound Cu2ZnSnSe4 is an excellent thermoelectric material. This inspires us to seek the other quaternary compounds with similar chemical formula to Cu2ZnSnSe4 as thermoelectric materials. In this paper, we use the first-principle method to systematically explore the electronic and phonon structures, mechanical, thermal and thermoelectric properties of p- and n-type Ag2XYSe4 (X=Ba, Sr; Y=Sn, Ge). It is found that the ZT maximum for n-type Ag2SrGeSe4 can reach up to 1.22 at 900 K, and those for p-type Ag2SrSnSe4, Ag2SrGeSe4 and Ag2BaSnSe4 can…
Thermoelectricity is a promising avenue for harvesting energy but large-scale applications are still hampered by the lack of highly-efficient low-cost materials. Recently, Fe$_2YZ$ Heusler compounds were predicted theoretically to be interesting candidates with large thermoelectric power factor. Here, we show that under doping conditions compatible with thermoelectric applications, these materials are prone to an unexpected magnetic instability detrimental to their thermoelectric performance. We rationalize the physics at the origin of this instability, provide guidelines for avoiding it and d…
Pressure-induced Superconductivity in Zintl Topological Insulator SrIn2As2
本研究通过ARPES实验证实SrIn2As2为强拓扑绝缘体，并发现压力可诱导其出现超导电性，为拓扑与超导关系提供关键见解。
The electronic and transport properties of the half-Heusler compound LaPtSb are investigated by performing first-principles calculations combined with semi-classical Boltzmann theory and deformation potential theory. Compared with many typical half-Heusler compounds, the LaPtSb exhibits obviously larger power factor at room temperature, especially for the n-type system. Together with the very low lattice thermal conductivity, the thermoelectric figure of merit (ZT) of LaPtSb can be optimized to a record high value of 2.2 by fine tuning the carrier concentration.
Improving the thermoelectric efficiency is one of the greatest challenges in materials science. The recent discovery of excellent thermoelectric performance in simple orthorhombic SnSe crystal offers new promise in this prospect [Zhao et al. Nature 508, 373 (2014)]. By calculating the thermoelectric properties of orthorhombic IV-VI compounds GeS,GeSe,SnS,and SnSe based on the first-principles combined with the Boltzmann transport theory, we show that the Seebeck coefficient, electrical conductivity, and thermal conductivity of orthorhombic SnSe are in agreement with the recent experiment. Impo…
We have performed systematic density functional calculations and evaluated thermoelectric properties, See- beck coefficient and anomalous Nernst coefficient of half-Heusler comounds CoMSb(M=Sc, Ti, V, Cr, and Mn). The carrier concentration dependence of Seebeck coefficients in nonmagnetic compounds are in good agreement with experimental values. We found that the half-metallic ferromagnetic CoMnSb show large anomalous Nernst effect originating from Berry curvature at the Brillouin zone boundary. These results help to understanding for the mechanism of large anomalous Nernst coefficient and giv…
The layered Bi-chalcogenide compounds have been drawing much attention as a new layered superconductor family since 2012. Due to the rich variation of crystal structure and constituent elements, the development of new physics and chemistry of the layered Bi-chalcogenide family and its applications as functional materials have been expected. Recently, it was revealed that the layered Bi chalcogenides can show a relatively high thermoelectric performance (ZT = 0.36 in LaOBiSSe at ~650 K). Here, we show the crystal structure variation of the Bi-chalcogenide family and their thermoelectric propert…
In order to improve the thermoelectric performance of TiCoSb we have substituted 50% of Ti equally with Zr and Hf at Ti site and Sb with Sn and Se equally at Sb site. The electronic structure of Ti0.5Zr0.25Hf0.25CoSn0.5Se0.5 is investigated using the full potential linearized augmented plane wave method and the thermoelectric transport properties are calculated on the basis of semi-classical Boltzmann transport theory. Our band structure calculations show that Ti0.5Zr0.25Hf0.25CoSn0.5Se0.5 has semiconducting behavior with indirect band gap value of 0.98 eV which follow the empirical rule of 18…
Electronic Transport and Fermi Surface Topology of Zintl Phase Compound SrZn2Ge2
本研究综合探究Zintl相化合物SrZn₂Ge₂单晶的电子输运性质与费米面拓扑，发现低温电阻率平台、磁阻交叉等现象，结合第一性原理计算证实其存在非平庸拓扑表面态与特殊费米面结构，为理解其输运机制提供关键依据。
We present a study of the electronic properties of Tl5Te3, BiTl9Te6 and SbTl9Te6 compounds by means of density functional theory based calculations. The optimized lattice constants of the compounds are in good agreement with the experimental data. The band gap of BiTl9Te6 and SbTl9Te6 compounds are found to be equal to 0.589 eV and 0.538 eV, respectively and are in agreement with the available experimental data. To compare the thermoelectric properties of the different compounds we calculate their thermopower using Mott's law and show, as expected experimentally, that the substituted telluride…
The electronic and transport properties of CuInTe2 chalcopyrite are investigated using density functional calculations combined with Boltzmann theory. The band gap predicted from hybrid functional is 0.92 eV, which agrees well with experimental data and leads to relatively larger Seebeck coefficient compared with those of narrow-gap thermoelectric materials. By fine tuning the carrier concentration, the electrical conductivity and power factor of the system can be significantly optimized. Together with the inherent low thermal conductivity, the ZT values of CuInTe2 compound can be enhanced to …
We report the structural, mechanical, electronic, optical, thermoelectric properties and spectroscopic limited maximum efficiency (SLME) of oxide double perovskite structure Ba2SbNbO6 and Ba2SbTaO6 compounds. All the investigations were performed through the first-principles density functional theory (DFT). The obtained values for the elastic constants reveal the mechanical stability of the studied compounds. The calculated data of bulk modulus (B), shear modulus (G), and Young's modulus (E) for Ba2SbTaO6 are found to be greater than those of Ba2SbNbO6. The ratio of Bulk to shear ratio (B/G) s…
Crystallographic data and thermoelectric properties (from 240 K up to 380 K) of Yb3Co4Ge13, Yb3Co4Sn13 compounds and Yb2CeCo4Ge13 and Yb2.3La0.7Co4Ge13 solid solutions are reported. The Seebeck coefficients, electric resistance and thermal conductivity increase monotonically with increasing temperature from 240 to 380 K for all the compounds. The Seebeck coefficient is S = 14 - 27 μV//K for Yb3Co4Sn13, and S = -21 -- -12 μV/K for Yb3Co4Ge13. The substitution of Yb for cerium or lanthanum in Yb3Co4Ge13 shifts the Seeebeck coefficient to positive values. The Yb3Co4Sn13 has a maximal ZT parameter…
Half-Heusler compounds usually exhibit relatively higher lattice thermal conductivity that is undesirable for thermoelectric applications. Here we demonstrate by first-principles calculations and Boltzmann transport theory that the BiBaK system is an exception, which has rather low thermal conductivity as evidenced by very small phonon group velocity and relaxation time. Detailed analysis indicates that the heavy Bi and Ba atoms form a cage-like structure, inside which the light K atom rattles with larger atomic displacement parameters. In combination with its good electronic transport propert…
Thermoelectric power generation has been recognized as one of the most important technologies, and high-performance thermoelectric materials have long been pursued. However, because of the large number of candidate materials, this quest is extremely challenging, and it has become clear that a firm theoretical concept from the viewpoint of band-structure engineering is needed. In this study, we theoretically demonstrate that pnictogen-dichalcogenide layered compounds, which originally attracted attention as a family of superconductors and have recently been investigated as thermoelectric materi…
High-throughput calculations are a very promising tool for screening a large number of compounds in order to discover new useful materials. Ternary intermetallic are thus investigated in the present work to find new compounds potentially interesting for thermoelectric applications. The screening of the stable non-metallic compounds required for such applications is obtained by calculating their electronic structure by DFT methods. In a first part, the study of the density of states at the Fermi level of well-known chemical elements and binary compounds allows to empirically optimize the select…
The discovery of Heusler alloys has revolutionized the research field of intermetallics due to the ease with which one can derive potential candidates for multifunctional applications. During recent years, many half Heusler alloys have been investigated for their thermoelectric properties. The f electron based rare earth ternary half Heusler compound DyPdBi has its f energy levels located close to the Fermi energy level. Other research efforts have emphasized that such materials have good thermoelectric capabilities. We have explored using first principles the electronic band structure of DyPd…
The copper silver selenide has two phases: the low-temperature semimetal phase (α-CuAgSe) and high-temperature phonon-glass superionic phase (\b{eta}-CuAgSe). In this work, the electric transport and thermoelectric properties of the two phases are investigated. It is revealed that the \b{eta}-CuAgSe is a p-type semiconductor and exhibits low thermal conductivity while the α-CuAgSe shows metallic conduction with dominant n-type carriers and low electrical resistivity. The thermoelectric figure of merit zT of the polycrystalline \b{eta}-CuAgSe at 623 K is ~0.95, suggesting that superionic CuAgSe…
We found that whisker crystals of Mo-doped Nb4SiTe4 show high thermoelectric performances at low temperatures, indicated by the largest power factor of 70 microW cm-1 K-2 at 230-300 K, much larger than those of Bi2Te3-based practical materials. This power factor is smaller than the maximum value in the 5d analogue Ta4SiTe4, but is comparable to that with a similar doping level. First principles calculation results suggest that the difference in thermoelectric performances between Nb and Ta compounds is caused by the much smaller band gap in Nb4SiTe4 than that in Ta4SiTe4, due to the weaker spi…
Thermoelectric transport in Ru$_2$TiSi full-Heusler compounds
本研究结合理论与实验探究Ru$_2$TiSi基全赫斯勒化合物的热电输运特性，发现其可用双抛物带模型描述，p型材料因轻空穴具更高效率，通过调控热导率有望实现zT>1的优异热电性能。
Although SbSe2-based layered compounds have been predicted to be high-performance thermoelectric materials and topological materials, most of these compounds obtained experimentally have been insulators so far. Here, we present the effect of Bi substitution on the thermoelectric properties of SbSe2-based layered compounds NdO0.8F0.2Sb1-xBixSe2 (x = 0-0.4). The room temperature electrical resistivity is decreased to 8.0 * 10^-5 ohmm for x = 0.4. The electrical power factor is calculated to be 1.4 * 10^-4 W/mK^2 at 660 K, which is in reasonable agreement with combined Jonker and Ioffe analysis. …
It is generally assumed in the thermoelectric community that the lattice thermal conductivity of a given material is independent of the electronic properties. This perspective is however questionable since the electron-phonon coupling could have certain effects on both the carrier and phonon transport, which in turn will affect the thermoelectric properties. Using SiGe compound as a prototypical example, we give an accurate prediction of the carrier relaxation time by considering scattering from all the phonon modes, as opposed to the simple deformation potential theory. It is found that the c…
Recently SnSe compound was reported to have a peak thermoelectric figure-5 of-merit (ZT) of 2.62 at 923 K, but the ZT values at temperatures below 750 K are relatively low. In this work, the electronic structures of SnSe are calculated using the density functional theory, and the electro- and thermo-transport properties upon varying chemical potential (or carrier density) are evaluated by the semi-classic Boltzmann transport theory, showing that the calculated ZT values along the a10 and c-axes below 675 K are in agreement with reported values, but that along the b-axis can be as high as 2.57 …
LaOBiPbS$_3$ is a kind of pnictogen-dichalcogenide layered compounds, which have recently been experimentally investigated as thermoelectric materials owing to their low thermal conductivity and high controllability of constituent elements. However, thermoelectric performance of LaOBiPbS$_3$ is at present not very high and that of its analogous compounds remains to be unknown. In this study, we theoretically investigate thermoelectric properties of 24 possible variations of the constituent elements in LaOBiPbS$_3$ from the viewpoint of the electronic structure. We find that some compounds can …
We explore the structural, electronic, mechanical and thermoelectric properties of a new half Heusler compound, HfPtPb which is all metallic heavy element and has been recently been proposed to be stable [Nature Chem 7 (2015) 308]. In the present work, we employ density functional theory and semiclassical Boltzmann transport equations with constant relaxation time approximation. The mechanical properties such as Shear modulus, Young modulus, elastic constants, Poisson ratio, and shear anisotropy factor are investigated. The elastic and phonon properties reveal that this compound is mechanicall…
Half-Heusler phases (space group F43m, C1b) have recently captured much attention as promising thermoelectric materials for heat-to-electric power conversion in the mid-to-high temperature range. The most studied ones are the RNiSn-type half-Heusler compounds, where R represents refractory metals Hf, Zr, and Ti. These compounds have shown a high-power factor and high-power density, as well as good material stability and scalability. Due to their high thermal conductivity, however, the dimensionless figure of merit (zT) of these materials has stagnated near 1 for a long time. Since 2013, the ve…
By using ab initio electronic structure calculations here we report the three new full Heusler alloys which are possessing very good thermoelectric behavior and expected to be synthesized in the laboratories. These are Fe2 ScP, Fe2 ScAs and Fe2 ScSb compound. First two compounds are indirect band gap semiconductors and the last one shows semimetallic ground state. The value of band gap of Fe2 ScP and Fe2 ScAs is 0.3 and 0.09 eV, respectively. These compounds show the presence of flat conduction bands along Γ - X-direction suggesting for the large electron like effective mass and promising for …
Determining defect types and concentrations remains a big challenge of semiconductor materials science. By using ab-initio thermal conductivity calculations we reveal that Ni/vacancy antisites, and not the previously claimed Sn/Zr antisites, are the dominant defects affecting thermal transport in half-Heusler compound ZrNiSn. Our calculations correctly predict the thermal conductivity dependence with temperature and concentration, in quantitative agreement with published experimental results. Furthermore, we find a characteristic proportionality between phonon-antisite scattering rates and the…
Half-Heusler compounds have emerged as promising thermoelectric materials that offer huge compositional space to tune their thermoelectric performance. A class of stable half Heusler compounds formed from elements of three specific groups in the periodic table viz. X$_{p}$X$'_{1-p}$Y$_{q}$Y$'_{1-q}$Z$_{r}$Z$'_{1-r}$ (with X, X$'$= Ti, Zr, Hf, Y, Y$'$ = Ni, Pd, Pt and Z, Z$'$ = Ge, Sn, Pb and p, q, r = 0, 0.25, 0.75 and 1) via various stoichiometric isoelectronic elemental substitution at the X, Y and Z sites respectively is investigated. Intelligent filters are employed at each step of our hig…
We present a study of the thermodynamic and physical properties of Tl5Te3, BiTl9Te6 and SbTl9Te6 compounds by means of density functional theory based calculations. The optimized lattice constants of the compounds are in good agreement with the experimental data. The electronic density of states and band structures are calculated to understand the bonding mechanism in the three compounds. The indirect band gap of BiTl9Te6 and SbTl9Te6 compounds are found to be equal to 0.256 eV and 0.374 eV, respectively. The spin-orbit coupling has important effects on the electronic structure of the two semi…
In the present work, we report the experimental thermopower ($α$) data for ZnV$_{2}$O$_{4}$ compound in the high temperature range 300-600 K. The value of $α$ is found to be $\sim$184 and $\sim$126 $μ$V/K at $\sim$300 and $\sim$600 K, respectively. The temperature dependent behavior of $α$ is almost linear in the measured temperature range. To understand the large and positive $α$ value observed in this compound, we have also investigated the electronic and thermoelectric properties by combining the \textit{ab-initio} electronic structures calculations with Boltzmann transport theory. Within t…
A finite electronic band gap is a standard filter in high-throughput screening of materials using density functional theory (DFT). However, because of the systematic underestimation of band gaps in standard DFT approximations, a number of compounds may incorrectly be predicted metallic. In a more accurate treatment, such materials may instead appear as low band gap materials and could e.g. have good thermoelectric properties if suitable doping is feasible. To explore this possibility, we performed hybrid functional calculations on 1093 cubic materials listed in the MaterialsProjects database w…
We have performed a comprehensive set of first principles calculations to study the structural, elastic, electronic, magnetic and transport properties of new quaternary Heusler compounds CoZrMnX (X =Al, Ga, Ge, In). The results showed that all the quaternary Heusler compounds were stable in Type(I) structure. CoZrMnX are elastically stable and relatively hard materials. CoZrMnAl, CoZrMnGa, and CoZrMnIn are found to be ductile and CoZrMnGe is brittle in nature. The calculated Debye temperatures of all compounds are relatively high. The electronic structure calculations reveal that CoZrMnAl is n…
Half-Heusler (HH) alloys have attracted considerable interest as promising thermoelectric (TE) materials in the temperature range around 700 K and above, which is close to the temperature range of most industrial waste heat sources. The past few years have seen nanostructuing play an important role in significantly enhancing the TE performance of several HH alloys. In this article, we briefly review the recent progress and advances in these HH nanocomposites. We begin by presenting the structure of HH alloys and the different strategies that have been utilized for improving the TE properties o…
Type-I clathrate compounds have attracted a great deal of interest in connection with the search for efficient thermoelectric materials. These compounds constitute networked cages consisting of nano-scale tetrakaidecahedrons (14 hedrons) and dodecahedrons (12 hedrons), in which the group 1 or 2 elements in the periodic table are encaged as the so-called rattling guest atom. It is remarkable that, though these compounds have crystalline cubic-structure, they exhibit glass-like phonon thermal conductivity over the whole temperature range depending on the states of rattling guest atoms in the tet…
We analyze the anisotropic electrical and thermal transport measurements in single crystals of In2Te5 belonging to monoclinic space group C12 c1 with the temperature gradient applied parallel and perpendicular to the crystallographic c-axis of the crystals. The thermal conductivity along the c-axis thermal conductivity parallel was found to smaller by a factor of 2 compared to the thermal conductivity along the direction perpendicular to the c-axis over the entire temperature range. In contrast, the Seebeck coefficient along the c-axis parallel was found to be higher than its value along the d…
Linear magnetoelectricity in the Zintl phase pnictides (Ba, Ca, Sr)$\mathrm{Mn}_2\mathrm{(P, As, Sb)}_2$ from first principles calculations
本研究利用密度泛函理论计算系统揭示Zintl相层状锰磷族化合物的线性磁电张量，阐明自旋与轨道、电子与晶格贡献，并发现其磁电响应可超过Cr₂O₃且受强关联影响。
Perovskite compounds have the potential to harvest solar energy as well as exploit the thermoelectric potential of a number of available materials. Here, we present the electronic, structural, thermoelectric, and optical properties of Cs2AgSbX6 (X = Cl, Br, I) perovskite with the help of the density functional theory (DFT). The WC-GGA approximation was used to calculate the structural parameters. All these compounds crystalize in a cubic unit cell with lattice constant increasing from 10.65 Å (Cl) to 11.14 Å (Br) to 11.86 Å (I). The mBJ-functional shows a semiconducting nature for these compou…
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