New Thermoelectric Materials with Precisely Determined Electronic Structure and Phonon Dispersion

2017 ◽  
pp. 115-141
Author(s):  
Tsunehiro Takeuchi
Keyword(s):  
Electronic Structure ◽  
Thermoelectric Materials ◽  
Phonon Dispersion

A first principles study of the phonon anharmonicity, electronic structure and optical characteristics of LaAlO3

2018 ◽  
Vol 1 (1) ◽  
pp. 161-180 ◽  
Author(s):  
Bahaa Ilyas ◽  
Badal Elias
Keyword(s):  
Thermal Conductivity ◽  
Electronic Structure ◽  
Ab Initio ◽  
Conversion Efficiency ◽  
First Principles ◽  
Phonon Scattering ◽  
Phonon Dispersion ◽  
Optical Spectra ◽  
Hybrid Functional ◽  
The Way

The way elementary excitations work together with their couplings and interact as condensed matter systems is very important when designing optimum energy-conversion devices. We investigated the electronic structure of LaAlO3, and we show that the bandgap insulator of LaAlO3 obtained theoretically by the hybrid functional HSE06 is an indirect 5.649eV that show a very good agreement with experimental data. The lattice constant is obtained exactly as experiment. In thermos-electric materials, the concept of conversion-efficiency (heat to electricity) is improved instantly by suppressing the phonon quasi-particles propagations that are responsible for draft macroscopic thermal transport. The material presented here for thermo-electric conversion-efficiency of cubic perovskite LaAlO3, show that it has an ultralow thermal-conductivity, while the formalism to its strong phonon scattering interactions resides mostly unclear. From the bases of Ab-initio simulations, the 4-dimensional phonon-dispersion surfaces of the cubic perovskite LaAlO3, have been mapped and we found that the origins of the ionic potential an-harmonicity being responsible for the unique behaviour and properties of LaAlO3. It is investigated that these phonon scattering arise solely from the LaAlO3 unstable electronic-structure, with its orbital interactions resulting to lattice instability similar to the ferroelectric instabilities. Our results show a microscopic insight bonding electronic-structure and phonon an-harmonicity in LaAlO3, and provides some new picture the way interactions happen between phonon–electron and phonon–phonon this lead to understand the concept of ultralow thermal-conductivity. Ab-initio calculations was performed on cubic perovskite LaAlO3 to obtain the phonon density of states (DOS) from 50 K to 5000 K, we find that the anharmonic behaviour starts around temperature limits of 500 K. The computed optical spectra were obtained using both the Beth Slapter Equation BSE and compared with the perturbed method using HSE06, optical spectra show that the inter-band transition occur precisely from the O-valence bands to the La-conduction bands throughout the low energy area. The energy-loss spectrum, optical conductivity and reflectivity and the refractive index are computed from first principles by using HSE06 hybrid functional. The optical band gap of material shows about 6.21 eV, which agrees with some cited experimental measurements.

Electronic structure of Heusler-type Fe 2 V 1+x Al 1−x thermoelectric materials

2014 ◽  
Vol 195 ◽  
pp. 185-188 ◽  
Author(s):  
Hidetoshi Miyazaki ◽  
Krystel Renard ◽  
Manabu Inukai ◽  
Kazuo Soda ◽  
Yoichi Nishino
Keyword(s):  
Electronic Structure ◽  
Thermoelectric Materials

Ab Initio Study of the Phonon Frequency, Electrical and Thermal Properties of TiN

2012 ◽  
Vol 155-156 ◽  
pp. 291-297
Author(s):  
Xin Tan ◽  
Yu Qing Li ◽  
Xue Jie Liu
Keyword(s):  
Electronic Structure ◽  
Thermal Properties ◽  
Specific Heat ◽  
Density Functional ◽  
Correlation Energy ◽  
Phonon Dispersion ◽  
Harmonic Approximation ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Phonon Spectra

With a motivation to understand microscopic aspects of TiN relevant to the electronic structure, phonon and thermal properties of transition metal nitride TiN superlattices, we determine its electronic structure, phonon spectra and thermal properties using first-principles calculations based on density functional theory with a generalized gradient approximation of the exchange correlation energy. We find that the electronic bands crossed by EF are half occupied, TiN has the ability of taking part in chemical reactions and also has the surface activity; A large gap in its phonon spectra, anomalies in the phonon dispersion of metallic TiN, manifested as dips in acoustic branches, but it do not contain soft modes in any direction; The specific heat (Cv) of TiN rises rapidly at low temperatures, the Cv values of the material, is identical to the Dulong-Petit value at high temperatures. Under the quasi-harmonic approximation (QHA), the thermal expansion, specific heat and bulk modulus B(T) are obtained, and the B(T) decreases along with the increase of temperature.

Electronic structure and optical properties of CsSnI3−yBry (y = 0, 1, 2, 3) perovskites

2019 ◽  
Vol 33 (04) ◽  
pp. 1950003 ◽  
Author(s):  
R. Padmavathy ◽  
A. Amudhavalli ◽  
R. Rajeswarapalanichamy ◽  
K. Iyakutti
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Density Functional ◽  
Energy Gap ◽  
Phonon Dispersion ◽  
Bromine Atom ◽  
Low Cost ◽  
Normal Pressure ◽  
Metallic Phase ◽  
Halide Perovskites

The halide perovskites-based solar cells have been attractive due to their excellent power conversion efficiency and low cost. The structural, electronic and optical properties of Sn-based cesium halide perovskites CsSnI[Formula: see text]Br[Formula: see text] (y = 0, 1, 2, 3) are investigated based on density functional theory. The computed electronic structure profile of CsSnI[Formula: see text]Br[Formula: see text] (y = 0, 1, 2, 3) reveals that these materials exhibit semiconducting behavior at normal pressure. The energy gap of CsSnI3 is tuned by the substitution of bromine atom for iodine atom. Also, it is found that the energy gap values of these materials decrease with increase in pressure and a semiconductor to metallic phase transition is observed at high pressure. The optical properties of these Sn-based halide perovskite compounds against the incident photon energy radiation indicate that these materials can be effective candidates for solar cell applications. The dynamical stability of these perovskites is analyzed by phonon dispersion curve.

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