The Effect of Point Defects on the Electronic Density of States of ScMN2-Type (M = V, Nb, Ta) Phases

ScMN2-type (M = V, Nb, Ta) phases are layered materials that have been experimentally reported for M = Ta and Nb. They are narrow-bandgap semiconductors with potentially interesting thermoelectric properties. Point defects such as dopants and vacancies largely affect these properties, motivating the need to investigate these effects. In particular, asymmetric peak features in the density of states (DOS) close to the highest occupied state is expected to increase the Seebeck coefficient. Here, we used first principles calculations to study the effects of one vacancy or one C, O, or F dopant on the DOS of the ScMN2 phases. We used density functional theory to calculate formation energy and the density of states when a point defect is introduced in the structures. In the DOS, asymmetric peak features close to the highest occupied state were found as a result of having a vacancy in all three phases. Furthermore, one C dopant in ScTaN2, ScNbN2, and ScVN2 implies a shift of the highest occupied state into the valence band, while one O or F dopant causes a shift of the highest occupied state into the conduction band.

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Effect of point defects on the electronic density of states of ScN studied by first-principles calculations and implications for thermoelectric properties

Physical Review B ◽

10.1103/physrevb.86.195140 ◽

2012 ◽

Vol 86 (19) ◽

Cited By ~ 51

Author(s):

Sit Kerdsongpanya ◽

Björn Alling ◽

Per Eklund

Keyword(s):

Thermoelectric Properties ◽

Density Of States ◽

Point Defects ◽

First Principles ◽

First Principles Calculations ◽

Electronic Density ◽

Electronic Density Of States

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Electronic structure and elastic properties of AgZn under pressure from first-principles calculations

Canadian Journal of Physics ◽

10.1139/cjp-2015-0684 ◽

2016 ◽

Vol 94 (3) ◽

pp. 328-333

Author(s):

Yasemin Ö. Çiftci

Keyword(s):

Density Of States ◽

First Principles ◽

Density Functional ◽

Elastic Stiffness ◽

Distribution Analysis ◽

First Principles Calculations ◽

Generalized Gradient ◽

Functional Theory ◽

B2 Structure ◽

Bonding Characteristic

In this study, the structural, elastic, electronic, and bonding nature of AgZn in B2 structure under pressure have been investigated by performing first principles calculations using density functional theory. The exchange-correlation potentials were treated within the generalized gradient approximation. The calculated quantities agree well with the available results. The electronic properties, such as band structure and density of states reveal that AgZn is metallic in nature with a large overlap at the Fermi level. The single-crystal elastic stiffness constants of AgZn are investigated using the stress–strain method. Present results for elastic constants show that AgZn is mechanically stable. The chemical bonding is interpreted by calculating the density of states and electron density distribution analysis. AgZn has ionic bonding characteristic.

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Properties of Cmc21-X2As2O (X = Si, Ge, and Sn) by First-Principles Calculations

Zeitschrift für Naturforschung A ◽

10.1515/zna-2018-0151 ◽

2018 ◽

Vol 73 (11) ◽

pp. 1025-1035 ◽

Cited By ~ 4

Author(s):

Ruike Yang ◽

Yucan Ma ◽

Qun Wei ◽

Dongyun Zhang

Keyword(s):

Density Functional ◽

Phonon Dispersion ◽

Dielectric Constants ◽

First Principles Calculations ◽

Hybrid Functional ◽

Functional Theory ◽

Narrow Bandgap ◽

Bandgap Semiconductors ◽

Mechanical Strengths ◽

Static Dielectric Constants

AbstractFor the compounds Cmc21-X2As2O (X = Si, Ge, and Sn), the stabilities are verified by the elastic constants and the phonon dispersion spectra. The structural, mechanical, electronic, and optical properties are investigated by using density functional theory (DFT) calculations. For Cmc21-X2As2O, the mechanical strengths in the [100], [010], and [001] directions are studied. Young’s modulus for Cmc21-Ge2As2O is more anisotropic than that of Cmc21-Si2As2O and Cmc21-Sn2As2O. The band structures of Cmc21-Si2As2O and Cmc21-Sn2As2O show that they are indirect-bandgap semiconductors with bandgaps of 2.744 and 2.201 eV, by using the HSE06 hybrid functional. Cmc21-Ge2As2O is a direct narrow-bandgap semiconductor with a bandgap of 2.131 eV. The static dielectric constants of Cmc21-Si2As2O and Cmc21-Sn2As2O in the [001] direction are higher than those in the [100] and [010] directions. The static dielectric constant of Cmc21-Ge2As2O in the [001] direction is lower than those in the [100] and [010] directions.

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First-Principles Calculations of the Structure and Magnetic Phases of FeAs2 Compound under Pressure

SPIN ◽

10.1142/s2010324718500169 ◽

2018 ◽

Vol 08 (04) ◽

pp. 1850016 ◽

Cited By ~ 1

Author(s):

O. Sebaa ◽

Y. Zaoui ◽

K. O. Obodo ◽

H. Bendaoud ◽

L. Beldi ◽

...

Keyword(s):

Phase Transition ◽

First Principles ◽

Density Functional ◽

Stable Phase ◽

Spin Orbit Coupling ◽

First Principles Calculations ◽

Generalized Gradient ◽

Electronic Density ◽

Functional Theory ◽

Spin Ordering

Understanding of different magnetic configurations for the FeAs2 iron pnictide compound is carried out using first-principles studies based on spin density functional theory (DFT) within the generalized gradient approximation (GGA), including the spin–orbit coupling (SOC). The calculated stable phase is in the marcasite (Pnnm) with nonmagnetic spin-ordering. We find that the FeAs2 compound in the nonmagnetic (NM) marcasite phase undergoes pressure-induced phase transition to the antiferromagnetic (AFM1) marcasite phase at 12[Formula: see text]GPa, then to the AFM CuAl2 ([Formula: see text]4/mcm) phase at 63[Formula: see text]GPa. The phase transition is also accompanied by semiconducting (marcasite phase) to metallic (CuAl2 phase) transition. The calculated electronic density of states profile shows the hybridization of the Fe-3[Formula: see text] and As-4[Formula: see text] orbitals plays an important role in determining the electronic and magnetic characters of this compound. The associated phase transition results in increased Fe-3d orbitals around the Fermi energy level.

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First-Principles Study of the Structural Stability and Electronic and Elastic Properties of Helium inα-Zirconium

Advances in Condensed Matter Physics ◽

10.1155/2014/929750 ◽

2014 ◽

Vol 2014 ◽

pp. 1-8 ◽

Cited By ~ 7

Author(s):

Jian Zheng ◽

Huijun Zhang ◽

Xiaosong Zhou ◽

Jianhua Liang ◽

Liusi Sheng ◽

...

Keyword(s):

Density Functional Theory ◽

Elastic Properties ◽

Density Of States ◽

First Principles ◽

Octahedral Site ◽

Density Functional ◽

Formation Energy ◽

Interstitial Site ◽

First Principles Calculations ◽

Functional Theory

First-principles calculations within density functional theory have been performed to investigate the behaviors of helium inα-zirconium. The most favorable interstitial site for He inα-Zr is not an ordinary tetrahedral or octahedral site, but a basal octahedral site with a formation energy as low as 2.40 eV. The formation energy reduces to 1.25 eV in the presence of preexisting vacancies. The analysis on the density of states and the charge density has been carried out. In addition, the influences of He and small He-V complexes on the elastic properties have been studied. The He-V complexes have been found to greatly affect the elastic properties compared with He alone.

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Thermodynamic Stability, Thermoelectric, Elastic and Electronic Structure Properties of ScMN2-Type (M = V, Nb, Ta) Phases Studied by ab initio Calculations

Condensed Matter ◽

10.3390/condmat4020036 ◽

2019 ◽

Vol 4 (2) ◽

pp. 36 ◽

Cited By ~ 1

Author(s):

Robert Pilemalm ◽

Leonid Pourovskii ◽

Igor Mosyagin ◽

Sergei Simak ◽

Per Eklund

Keyword(s):

Thermoelectric Properties ◽

Thermodynamic Stability ◽

First Principles ◽

Density Functional ◽

Mixing Enthalpy ◽

First Principles Calculations ◽

Electronic Density ◽

Functional Theory ◽

Small Band ◽

Structure Properties

ScMN2-type (M = V, Nb, Ta) phases are layered materials that have been experimentally reported for M = Ta and Nb, but they have up to now not been much studied. However, based on the properties of binary ScN and its alloys, it is reasonable to expect these phases to be of relevance in a range of applications, including thermoelectrics. Here, we have used first-principles calculations to study their thermodynamic stability, elastic, thermoelectric and electronic properties. We have used density functional theory to calculate lattice parameters, the mixing enthalpy of formation and electronic density of states as well as the thermoelectric properties and elastic constants (cij), bulk (B), shear (G) and Young’s (E) modulus, which were compared with available experimental data. Our results indicate that the considered systems are thermodynamically and elastically stable and that all are semiconductors with small band gaps. All three materials display anisotropic thermoelectric properties and indicate the possibility to tune these properties by doping. In particular, ScVN2, featuring the largest band gap exhibits a particularly large and strongly doping-sensitive Seebeck coefficient.

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First Principles Calculations of the Formation Energy of the Neutral Vacancy in Germanium

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.131-133.241 ◽

2007 ◽

Vol 131-133 ◽

pp. 241-246 ◽

Cited By ~ 9

Author(s):

P. Śpiewak ◽

Krzysztof Jan Kurzydlowski ◽

Koji Sueoka ◽

Igor Romandic ◽

Jan Vanhellemont

Keyword(s):

Experimental Data ◽

Point Defects ◽

First Principles ◽

Density Functional ◽

Formation Energy ◽

Local Density ◽

Density Approximation ◽

First Principles Calculations ◽

Functional Theory ◽

Germanium Single Crystal

Density functional theory (DFT) with local density approximation has been used to calculate the formation energy (EF) of the neutral vacancy in germanium single crystal. It was shown that careful checking of convergence with respect to the number of k-points is necessary when calculating the formation energy of the intrinsic point defects in Ge. The formation energy of the single neutral vacancy was estimated at 2.35 eV which is in excellent agreement with published experimental data.

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Elastic Properties and Electronic Structures of L12-TiAl3 and L12-Ti(Al,Pt)3: A Density Functional Theory Investigation

Materials Science Forum ◽

10.4028/www.scientific.net/msf.817.816 ◽

2015 ◽

Vol 817 ◽

pp. 816-825

Author(s):

Bo Huang ◽

Yong Hua Duan ◽

Sun Yong ◽

Ming Jun Peng

Keyword(s):

Elastic Properties ◽

First Principles ◽

Electronic Structures ◽

Density Functional ◽

Structural Parameters ◽

First Principles Calculations ◽

Elastic Parameters ◽

Electronic Density ◽

Functional Theory ◽

Experimental Values

First-principles calculations have been carried out to investigate the elastic properties and electronic structures of L12-TiAl3and L12-Ti (Al, Pt)3. The optimized structural parameters were largely consistent with the experimental values. The electronic density of states (DOS) and the differences of charge density distribution were given. The independent single-crystal elastic constants and polycrystalline elastic parameters such as bulk modulusB, Young’s modulusE, shear modulusG, Poisson’s ratioνand anisotropy valueAhave been calculated by Voigt-Reuss-Hill averaging scheme. The results indicate that the L12-Ti (Al, Pt)3exhibits larger anisotropy and more ductile than L12-TiAl3.

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First-principles study on the electronic structure and elastic properties of Mo2NiB2 doped with V

Modern Physics Letters B ◽

10.1142/s0217984918500653 ◽

2018 ◽

Vol 32 (10) ◽

pp. 1850065 ◽

Cited By ~ 5

Author(s):

Jinming Li ◽

Xiaobo Li ◽

Haiyun Gao ◽

Dian Peng

Keyword(s):

Electronic Structure ◽

Elastic Properties ◽

Density Of States ◽

First Principles ◽

Density Functional ◽

Mechanical Stability ◽

Formation Enthalpy ◽

First Principles Calculations ◽

Functional Theory ◽

Ternary Boride

The content of this study is to analyze the electronic structure and elastic properties that the different structures of Mo2NiB2 and doping with V of the tetragonal M3B2 (Mo2Ni[Formula: see text]V[Formula: see text]B2 and Mo[Formula: see text]Ni[Formula: see text]V[Formula: see text]B2) (x = 0.25, 0.5, 0.75 and y = 0.125, 0.25, 0.375) by first-principles calculations based on density functional theory (DFT) combined with the projection-plus-wave method. But the calculated formation energy shows that V atoms prefer to substitute the Mo and Ni atoms of the tetragonal Mo2NiB2. Moreover, with the increase of V content, the formation enthalpy of tetragonal Mo2NiB2 is reduced, and the formation enthalpy of Mo[Formula: see text]Ni[Formula: see text]V[Formula: see text]B2 is the least as −53.23 kJ/mol. The calculated elastic constant suffices the condition of mechanical stability, indicate that they are stable. The calculated elastic modulus illustrates that Mo2NiB2 having better mechanical properties when V elements are at Mo and Ni sites instead of Ni sites. The calculated and analyzed density of states of Mo[Formula: see text]Ni[Formula: see text]V[Formula: see text]B2 has the smallest the density of states at the Fermi level indicating that it has the more stable structure. For the theoretical analysis of the first-principles calculations, the addition of 15 atom% of the V and V doping modes of Mo and Ni are preferentially replaced by V atoms of Mo2NiB2 ternary boride has the best performance.

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First-Principles Calculations of Transition Metal Nitrides TiN and NbN

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.150-151.174 ◽

2010 ◽

Vol 150-151 ◽

pp. 174-177 ◽

Cited By ~ 1

Author(s):

F.Y. Xue ◽

H.Y. Wang ◽

Nai Hui Zhao ◽

De Jun Li

Keyword(s):

Density Of States ◽

First Principles ◽

Density Functional ◽

Density Functional Theory Method ◽

First Principles Calculations ◽

Transition Metal Nitrides ◽

Functional Theory ◽

Pseudopotential Calculations ◽

Theoretical Results ◽

Good Agreement

First-principles study of elastic modulus, shear modulus and some other elastic parameters of TiN and NbN are reported using the plane-wave pseudopotential density functional theory method in this paper. The calculated lattice and elastic constants are in good agreement with the experimental data and other theoretical results. The band structure and density of states of these two compounds were obtained, which show that the mainly contribution on pseudopotential calculations of the density of states of TiN is Ti-3d orbital and N-2p orbital, while TiN is the Nb-4d orbit and B-2p orbit, TiN with higher conductivity; Pugh empirical criterion shows that TiN and NbN are both brittle compounds, and NbN is more brittle than TiN.

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