Elastic Constants and Fermi Surface Topology Change in Calaverite Aute 2: A Density Functional Study

Structural, elastic, electronic and Fermi surface studies of AuTe2 have been carried out by means of first principles calculations based on density functional theory. The calculated ground state properties agree well with the experiment. Fermi surface and elastic constants are predicted for the first time and from the calculated elastic constants we find the compound to be mechanically stable satisfying the stability criteria of monoclinic structure. In addition, we also find the c-axis to be more compressible than the other two which is also speculated from the present work. The metallic behaviour of this compound is confirmed from the electronic band structure calculation as we find the bands to cross the Fermi level (EF). In addition, we also observe a FS topology change under pressure which is also explained in the present wor

Predicted thermoelectric properties of olivine-type Fe(2)GeCh(4) (Ch = S, Se and Te)

We present here the thermoelectric properties of olivine-type Fe(2)GeCh(4) (Ch = S, Se and Te) using the linear augmented plane wave method based on first principles density functional calculations. The calculated transport properties using the semi-local Boltzmann transport equation reveal very high thermopower for both S and Se-based compounds compared to their Te counterparts. The main reason for this high thermopower is the quasi-flat nature of the bands at the valence and conduction band edges. The calculated thermopower of Fe2GeS4 is in good agreement with the experimental reports at room temperature, with the carrier concentration around 10(18)-10(19)cm(-3). All the investigated systems show an anisotropic nature in their electrical conductivity, resulting in a value less than the order of 10(2) along the a-axis compared to the b- and c-axes. Among the studied compounds, Fe2GeS4 and Fe2GeSe4 emerge as promising candidates with good thermoelectric performance

Thermoelectric properties of CuAlCh 2 (Ch = S, Se and Te)

Electronic and thermoelectric properties of ternary chalcopyrite-type CuAlCh 2 (S, Se and Te) were studied using the first principles density functional calculations implemented in the full potential linear augmented plane wave (FP-LAPW) method. The thermoelectric properties are calculated by solving the Boltzmann transport equation within the constant relaxation time approximation. The calculated band gap using the Tran-Blaha modified Becke-Johnson potential (TB-mBJ), of all the compounds are in good agreement with the available experiment and other theoretical reports. Thermoelectric properties like thermopower, electrical conductivity scaled by relaxation time are calculated as a function of carrier concentrations at different temperatures. The calculated thermoelectric properties are compared with the available experiment and other theoretical calculations of similar materials

CuAlTe2: A promising bulk thermoelectric material

Transport properties of Cu-based chalcopyrite materials are presented using the full potential linear augmented plane wave method and Boltzmann Semi-classical theory. All the studied compounds appear to be direct band gap semiconductors evaluated based on the Tran-Blaha modified Becke-Johnson potential. The heavy and light band combination found near the valence band maximum (VBM) drive these materials to possess good thermoelectric properties. Among the studied compounds, CuAlTe2 is found to be more promising, in comparison with CuGaTe2, which is reported to be an efficient thermoelectric material with appreciable figure of merit. Another interesting fact about CuAlTe2 is the comparable thermoelectric properties possessed by both n- type and p-type carriers, which might attract good device applications and are explained in detail using the electronic structure calculations

Structural and thermoelectric properties of Zintl-phase CaLiPn (Pn=As, Sb, Bi)

First-principles calculations were carried out to study the structural, mechanical, dynamical and transport properties of zintl phase materials CaLiPn (Pn=As, Sb and Bi). We have used two different approaches to solve the system based on density functional theory. The plane wave pseudopotential approach has been used to study the structural and dynamical properties whereas, full potential linear augment plane wave method is used to examine the electronic structure, mechanical and thermoelectric properties. The calculated ground-state properties agree quite well with experimental values. The computed electronic structure shows the investigated compounds to be direct band gap semiconductors. Further, we have calculated the thermoelectric properties of all the investigated compounds for both the carriers at various temperatures. We found a high thermopower for both the carriers, especially n-type doping to be more favourable, which enabled us to predict that CaLiPn might have promising applications as a good thermoelectric material. Further, the phonon dispersion curves of the investigated compounds showed flat phonon modes and we also find lower optical and acoustic modes to cut each other at the lower frequency range, which further indicate the investigated compounds to possess reasonably low thermal conductivity. We have also analysed the low value of the thermal conductivity through the empirical relations and discussions are presented here

Thermoelectric properties of marcasite and pyrite FeX2 (X = Se, Te): A first principle study

Electronic structure and thermoelectric properties of marcasite (m) and synthetic pyrite (p) phases of FeX2 (X = Se, Te) have been investigated using first principles density functional theory and Boltzmann transport equation. The plane wave pseudopotential approximation was used to study the structural properties and full-potential linear augmented plane wave method was used to obtain the electronic structure and thermoelectric properties (thermopower and power factor scaled by relaxation time). From total energy calculations we find that m-FeSe2 and m-FeTe2 are stable at ambient conditions and no structural transition from marcasite to pyrite is seen under the application of hydrostatic pressure. The calculated ground state structural properties agree quite well with available experiments. From the calculated thermoelectric properties, we find that both m and p forms are good candidates for thermoelectric applications. However, hole doped m-FeSe 2 appears to be the best among all the four systems

Thermoelectric properties of binary LnN (Ln=La and Lu): First principles study

First principles density functional calculations were carried out to study the electronic structure and thermoelectric properties of LnN (Ln = La and Lu) using the full potential linearized augmented plane wave (FP-LAPW) method. The thermoelectric properties were calculated by solving the Boltzmann transport equation within the constant relaxation time approximation. The obtained lattice parameters are in good agreement with the available experimental and other theoretical results. The calculated band gaps using the Tran-Blaha modified Becke-Johnson potential (TB-mBJ), of both compounds are in good agreement with the available experimental values. Thermoelectric properties like thermopower (S), electrical conductivity scaled by relaxation time (σ/τ) and power-factor (S2σ/τ) are calculated as functions of the carrier concentration and temperature for both compounds. The calculated thermoelectric properties are compared with the available experimental results of the similar material ScN

[082] 語文研究表紙奥付等

瀬里廣明著　『露伴と大拙 : 儒と禅と念仏の世界』柏原卓編　『和歌浦物語』白石良夫著　ちくま新書074『最後の江戸留守居役』藤井茂利著　『古代日本語の表記法研究 : 東アジアに於ける漢字の使用法比較』今西祐一郎校注　『蜻蛉日記』(岩波文庫

High Thermopower and Optical Properties of A 2

The current work analyzes the electronic, structural, mechanical, thermoelectric (TE), and optical properties of alkali-based transition metal chalcogenides (Formula presented.) (A = K, Rb, Cs) and (Formula presented.) using methods based on first principles. The electronic, structural, and mechanical properties are analyzed using projected augmented wave (PAW) potentials. The electronic structure calculations show them to be direct bandgap semiconductors. From the TE properties, it is found that all the compounds possess huge thermopower especially for the holes, and this along with low lattice thermal conductivity enables us to predict (Formula presented.) (A = K, Rb, Cs) and (Formula presented.) to be a good class of material for TE applications. Also, the optical properties are found to be nearly isotropic in the low energy region, which also might fetch potential applications in the visible range. The nearly isotropic optical properties along with giant thermopower are the highlights of the current study, which sets a platform for exploring future device applications