INVESTIGATION OF STRUCTURAL, ELECTRONIC AND THERMOELECTRIC PROPERTIES OF XCUOTE (X: BI, CE, LE) WITH GGA-WC EXCHANGE CORRELATION FUNCTIONAL

2016 ◽  
Vol 78 (3) ◽  
Author(s):  
Muhammad Azim Izzuddin Mohd Amin ◽  
R. Ahmed ◽  
A. Shaari ◽  
Bakhtiar Ul-Haq ◽  
Mazmira Mohamad ◽  
...  
Keyword(s):  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
Density Functional ◽  
Chemical Potential ◽  
Electronic Conductivity ◽  
Generalized Gradient ◽  
Exchange Correlation ◽  
Semi Empirical ◽  
Linearized Augmented Plane Wave ◽  
Good Agreement

Linearized augmented plane wave plus local orbitals (LAPW + lo) method designed within density functional theory (DFT) has been used in this study to calculate the structural, electronic and thermoelectric properties of XCuOTe (X=Bi, Ce, La). Generalized gradient approximation, Wu-Cohen (GGA-WC) parameterized exchange correlation functional, was used. The structural and electronic calculations have a good agreement with previous study. For thermoelectric calculation, semi empirical Boltzmann approach implemented in BoltzTraP package was used to calculate Seebeck coefficient, electronic conductivity as well as thermal conductivity. By referring to previous studies, the results have good agreement with them. In addition, the Seebeck coefficient of these materials was calculated as a function of the chemical potential at temperatures 300K, 600K, and 900K. Our calculations highlight suitability of these materials for applications in thermoelectric devices.

scholarly journals Structural, electronic and thermoelectric properties of the intermetallic materials based on Mg2X (X= Si, Ge, Sn): DFT calculations

2017 ◽  
Vol 2 (2) ◽  
pp. 25
Author(s):  
Miloud Ibrir
Keyword(s):  
Thermoelectric Properties ◽  
Density Functional ◽  
Local Density ◽  
Electronic Conductivity ◽  
Full Potential ◽  
Plane Wave Method ◽  
Intermetallic Materials ◽  
Merit Factor ◽  
Densities Of States ◽  
Linearized Augmented Plane Wave

The scope of this work is the investigation of the physical properties of chalcopyrite materials using ab-initio methods in order to simulate a new structure of thin-films photovoltaic cells with high conversion efficiency. In the first framework, we obtained the results of calculations based on Density Functional Theory (DFT) using the full-potential linearized augmented plane wave method (FP-LAPW) as involved in the WIEN2K computational package. For the exchange-correlation potential, the local density approximation (LDA) was used to calculate the lattice parameters, Bulk modulus and its first derivative as well as the densities of states of the intermetallic semiconductors materials based on Mg2X (X=Si, Ge and Sn). The semi-local Becke-Johnson (mBJ) potential and its modified form proposed by Tran and Blaha (TB-mBJ) were also used for studying the electronic and thermoelectric properties; (merit factor, Seebeck coefficient, electronic conductivity). The achieved results were compared to computational works and other data acquired experimentally.

Carrier and Transition Metals (M = Nb, Cr and Fe) Doping Effects on Structure and Electronic Structure in Spinel Li4Ti5O12 Compounds

2020 ◽  
Vol 310 ◽  
pp. 88-95
Author(s):  
Lkhagvajav Sarantuya ◽  
Namsrai Tsogbadrakh ◽  
Galsan Sevjidsuren ◽  
Pagvajav Altantsog
Keyword(s):  
Electronic Structure ◽  
Density Functional ◽  
Electronic Conductivity ◽  
Generalized Gradient ◽  
Promising Candidate ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Doping Effects ◽  
Li Ion ◽  
Projector Augmented Wave

Spinel Li4Ti5O12 (LTO) is one of the most promising candidate anode material for Li-ion battery (LIB) known, as zero strain material, it has poor intrinsic electronic properties. In order to enhance it, we have investigated effect of doping on electronic conductivity of spinel LTO phase structure. We consider the carrier and transition metal doping effect on structure and electronic structure of spinel LTO. It is shown that the doping can improve the electronic conduction of spinel LTO. Our calculations were based on the projector augmented wave (PAW) method with the generalized gradient approximation (GGA+U+J0) including the Hubbard U parameter for exchange correlation functional within the framework of density functional theory (DFT).

scholarly journals Spinelectronic investigation of the quaternary vanadium fluoride Rb2NaVF6: Ab-initio method

2020 ◽  
Vol 66 (5 Sept-Oct) ◽  
pp. 604
Author(s):  
M. Berber ◽  
N. Bouzouira ◽  
H. Abid ◽  
A. Boudali ◽  
H. Moujri
Keyword(s):  
Density Functional ◽  
Structural Parameters ◽  
Magnetic Moments ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Half Metallic ◽  
Exchange Correlation ◽  
Spin Polarized ◽  
Higher Temperature ◽  
Good Agreement

In this study, we have investigated the structural, electronic, and magnetic properties of the Rb2NaVF6 compound. We have performed our calculations by the use of first-principle methods based on spin-polarized density functional theory, where the electronic exchange-correlation potential is treated by the generalized gradient approximation GGA- PBEsol coupled with the improved TB-mBJ approach. The calculated structural parameters of Rb2NaVF6 are in good agreement with the available experimental data. Rb2NaVF6 exhibits a half-metallic ferromagnetic feature with a spin polarization of 100 % at the Fermi level and a direct large half-metallic gap of 3.582 eV. The total magnetic moments are 2 μB. This material is half-metallic ferromagnets, and it can be potential candidates for spintronics applications at a higher temperature.

Effect of K/Bi ordering on the electronic structure of K2Bi8Se13

2003 ◽  
Vol 793 ◽  
Author(s):  
Daniel I Bilc ◽  
Paul Larson ◽  
S.D. Mahanti ◽  
M.G. Kanatzidis
Keyword(s):  
Electronic Structure ◽  
Density Functional ◽  
Chemical Potential ◽  
Full Potential ◽  
Generalized Gradient ◽  
Ordered Structures ◽  
Β Phase ◽  
Indirect Band Gap ◽  
Flapw Method ◽  
Linearized Augmented Plane Wave

ABSTRACTK2Bi8Se13 belongs to a class of complex chalcogenides which show potential for superior thermoelectric performance. This compound forms in two distinct phases, α and β. The β-phase, which has several sites with mixed K/Bi occupancy is a better thermoelectric. To understand the origin of this difference we have carried out electronic structure calculations within ab initio density functional theory using full potential linearized augmented plane wave (FLAPW) method. The generalized gradient approximation was used to treat the exchange and correlation potential. Spin-orbit interaction (SOI) was incorporated using a second variational procedure. The α-phase is found to be a semiconductor with an indirect band gap of 0.47eV compared to 0.76eV for the observed direct optical gap. For the β-phase we have chosen two different ordered structures with full occupancies of K and Bi atoms at the “mixed sites”. The system is a semi-metal for both the ordered structures. To incorporate the effect of mixed occupancy we have chosen a 1x1x2 supercell with an alternative K/Bi occupancy at the “mixed sites”. The superlattice ordering gives a semiconductor with an indirect gap of 0.38eV. Mixed occupancy is crucial for the system to be a semiconductor because the Bi atoms at the “mixed sites” stabilize the p orbitals of the neighboring Se atoms by lowering their energy, and opening up a gap at the chemical potential.

Thermal Properties of Divalent Metal Oxides: CaO as a Prototype

2013 ◽  
Vol 209 ◽  
pp. 190-193
Author(s):  
Nisarg K. Bhatt ◽  
Brijmohan Y. Thakore ◽  
P.R. Vyas ◽  
A.Y. Vahora ◽  
Asvin R. Jani
Keyword(s):  
Density Functional ◽  
Tight Binding ◽  
Mean Field ◽  
Field Potential ◽  
Theoretical Data ◽  
Test Case ◽  
Generalized Gradient ◽  
Core Electrons ◽  
Vibrational Free Energy ◽  
Semi Empirical

Commonly employed quasiharmonic approximation (QHA) is inadequate to account for intrinsic anharmonism such as phonon-phonon interaction, vacancy contribution, etc. Though anharmonic contributions are important at high temperatures and low pressure, complete ab initio calculations are scanty due largely to laborious computational requirements. Nevertheless, some simple semi-empirical schemes can be used effectively to incorporate the anharmonism. In this regards, in the present study we have proposed a simple computational scheme to include the effect of vacancy directly into the description within the mean-field potential approach, which calculates vibrational free energy of ions. Validity of the scheme is verified by taking calcium oxide as a test case. Equilibrium properties at (T,P) = (0,0) condition is obtained within the tight-binding second-moment approximation (TB-SMA), whose parameters were determined through first principles density functional theory. Kohn-Sham equations for core electrons were solved using ultrasoft plane-wave pseudopotential employing the generalized gradient approximation for exchange and correlation. Present findings for thermal expansion and high-T EOS clearly show perceptible improvement over the case when vacancy contribution was not included. Some related thermodynamic properties are also calculated and compared with the available experimental and theoretical data.

Electronic structure of the thermoelectric materials PbTe and AgPb18SbTe20 from first-principles calculations

2010 ◽  
Vol 25 (6) ◽  
pp. 1030-1036 ◽  
Author(s):  
Pengxian Lu ◽  
Zigang Shen ◽  
Xing Hu
Keyword(s):  
Band Structure ◽  
Thermoelectric Properties ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Partial Density ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Scanning Transmission ◽  
Linearized Augmented Plane Wave

To investigate the effects of substituting Ag and Sb for Pb on the thermoelectric properties of PbTe, the electronic structures of PbTe and AgPb18SbTe20 were calculated by using the linearized augmented plane wave based on the density-functional theory of the first principles. By comparing the differences in the band structure, the partial density of states (PDOS), the scanning transmission microscope, and the electron density difference for PbTe and AgPb18SbTe20, we explained the reason from the aspect of electronic structures why the thermoelectric properties of AgPb18SbTe20 could be improved significantly. Our results suggest that the excellent thermoelectric properties of AgPb18SbTe20 should be attributed in part to the narrowing of its band gap, band structure anisotropy, the much extrema and large DOS near Fermi energy, as well as the large effective mass of electrons. Moreover, the complex bonding behaviors for which the strong bonds and the weak bonds are coexisted, and the electrovalence and covalence of Pb–Te bond are mixed should also play an important role in the enhancement of the thermoelectric properties of the AgPb18SbTe20.

Electronic Structure Of (AgSb)xPbn-2xTen

2003 ◽  
Vol 793 ◽  
Author(s):  
Daniel I Bilc ◽  
S.D. Mahanti ◽  
M.G. Kanatzidis
Keyword(s):  
Electronic Structure ◽  
Ab Initio ◽  
Density Functional ◽  
Full Potential ◽  
Generalized Gradient ◽  
Two Component System ◽  
Functional Theory ◽  
Covalent Interaction ◽  
Salt Structure ◽  
Linearized Augmented Plane Wave

ABSTRACTComplex quaternary chalcogenides (AgSb)xPbn-2xTen (0<x<n/2) are thought to be narrow band-gap semiconductors which are very good candidates for room and high temperature thermoelectric applications. These systems form in the rock-salt structure similar to the well known two component system PbTe (x=0). In these systems Ag and Sb occupy Pb sites randomly although there is some evidence of short-range order. To gain insights into the electronic structure of these compounds, we have performed electronic structure calculations in AgSbTe2 (x=n/2). These calculations were carried out within ab initio density functional theory (DFT) using full potential linearized augmented plane wave (LAPW) method. The generalized gradient approximation (GGA) was used to treat the exchange and correlation potential. Spinorbit interaction (SOI) was incorporated using a second variational procedure. Since it is difficult to treat disorder in ab initio calculations, we have used several ordered structures for AgSbTe2. All these structures show semimetallic behavior with a pseudogap near the Fermi energy. Te and Sb p orbitals, which are close in energy, hybridize rather strongly indicating a covalent interaction between Te and Sb atoms.

Density Functional Theory Approach for Muon Sites Estimation in Mn3Sn

2021 ◽  
Vol 1028 ◽  
pp. 199-203
Author(s):  
Fiqhri Heda Murdaka ◽  
Edi Suprayoga ◽  
Abdul Muizz Pradipto ◽  
Kohji Nakamura ◽  
Agustinus Agung Nugroho
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Local Density ◽  
Full Potential ◽  
Theory Approach ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Electrostatic Potential Calculation ◽  
A Site ◽  
Linearized Augmented Plane Wave

We report the estimation of muon sites inside Mn3Sn using density functional theory based on the full-potential linearized augmented plane wave (FLAPW) calculation. Our calculation shows that the Perdew–Burke–Ernzerhof (PBE) Generalized-Gradient Approximation (GGA) functional is closer to the experimental structure compared to the von Barth-Hedin Local Density Approximation (LDA)-optimized geometry. The PBE GGA is therefore subsequently used in FLAPW post-calculation for the electrostatic potential calculation to find the local minima position as a guiding strategy for estimating the muon site. Our result reveals at least two muon sites of which one is placed at the center between two Mn-Sn triangular layers (A site) and the other at the trigonal prismatic site of Sn atom (B site). The total energy of Mn3Sn system in the presence of muon at A site or B site are compared and we find that A site is a more favorable site for muon to stop.

First-Principles Studies of the Magnetic Properties of hcp Cr in Cr/Cu(111) and Cr/Ru(0001) Superlattices

2002 ◽  
Vol 721 ◽  
Author(s):  
G. Y. Guo
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Recent Observation ◽  
Theoretical Calculations ◽  
Ferromagnetic State ◽  
Full Potential ◽  
Generalized Gradient ◽  
Plane Wave Method ◽  
Wide Range ◽  
Linearized Augmented Plane Wave

AbstractLatest first-principles density functional theoretical calculations using the generalized gradient approximation and highly accurate all-eleectron full-potential linearized augmented plane wave method, show that bulk hcp Cr would be a paramagnet and that no ferromagnetic state could be stabilized over a wide range of volume [1]. To understand the recent observation of the weakly ferromagnetic state of Cr in hcp Cr/Ru (0001) superlattices [2], the same theoretical calculations have been carried out for the hcp Cr3/Ru7 (0001) and hcp Cr3/fcc Cu6 (111) superlattices. The Cr/Ru superlattice is found to be ferromagnetic with a small magnetic moment of ∼0.31μB/Cr while in contrast, Cr/Cu superlattice is found to be nonmagnetic.

Electronic structure of cubic BaTbO3 from first-principles pseudopotential calculations

2006 ◽  
Vol 84 (2) ◽  
pp. 115-120 ◽  
Author(s):  
G Y Gao ◽  
K L Yao ◽  
Z L Liu
Keyword(s):  
Electronic Structure ◽  
First Principles ◽  
Density Functional ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Pseudopotential Calculations ◽  
Correlation Potential ◽  
Density Contour

First-principles calculations of the electronic structure are performed for cubic BaTbO3 using the plane-wave pseudopotential method within the framework of density functional theory and using the generalized gradient approximation for the exchange-correlation potential. Our calculations show that cubic BaTbO3 is metallic, and that this metallic character is mainly governed by the Tb 4f electrons and the hybridization between the Tb 5d and O 2p states. From the analysis of the density of states, band structure, and charge density contour, we find that the chemical bonding between Tb and O is covalent while that between Ba and TbO3 is ionic. PACS Nos.: 71.15.Mb, 71.20.-b

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