Theoretical investigation of elastic and phononic properties of Zn1−xBexO alloys

2015 ◽  
Vol 29 (24) ◽  
pp. 1550140 ◽  
Author(s):  
F. Elhamra ◽  
S. Lakel ◽  
M. Ibrir ◽  
K. Almi ◽  
H. Meradji
Keyword(s):  
Density Functional ◽  
Phonon Dispersion ◽  
Local Density ◽  
Molar Fraction ◽  
Dielectric Constants ◽  
Functional Theory ◽  
Phonon Dispersion Curves ◽  
Density Functional Perturbation Theory ◽  
Pseudo Potential ◽  
Born Effective Charge

Our calculations were conducted within density functional theory (DFT) and density functional perturbation theory (DFPT) using norm-conserving pseudo-potential and the local density approximation. The elastic constants of [Formula: see text] were calculated, [Formula: see text], [Formula: see text] and [Formula: see text] increase with the increase of Be content, whereas the [Formula: see text] shows a non-monotonic variation and [Formula: see text] decreases when Be concentration increases. The values of bulk modulus [Formula: see text], Young’s modulus [Formula: see text] and shear modulus [Formula: see text] increase with the increase of Be content. Poisson’s ratio [Formula: see text] decreases with increased Be concentration. The ductility decreases with increasing Be concentration and the compressibility for [Formula: see text] along [Formula: see text]-axis is smaller than along [Formula: see text]-axis. Phonon dispersion curves show that [Formula: see text] is dynamically stable (no soft modes). Quantities such as refractive index, Born effective charge, dielectric constants and optical phonon frequencies were calculated as a function of the Be molar fraction [Formula: see text]. The agreement between the present results and the known data that are available only for ZnO and BeO is generally satisfactory. Our results for [Formula: see text] [Formula: see text] are predictions.

AB INITIO STUDY OF PHONON DISPERSION AND ELASTIC PROPERTIES OF L12 INTERMETALLICS Ti3Al AND Y3Al

2013 ◽  
Vol 27 (30) ◽  
pp. 1350224 ◽  
Author(s):  
N. ARIKAN ◽  
M. ERSEN ◽  
H. Y. OCAK ◽  
A. İYIGÖR ◽  
A. CANDAN ◽  
...  
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Phonon Dispersion ◽  
High Symmetry ◽  
Generalized Gradient ◽  
Pressure Derivative ◽  
Phonon Dispersion Curves ◽  
Lattice Constants ◽  
Density Functional Perturbation Theory ◽  
Phonon Properties

In this paper, the structural, elastic and phonon properties of Ti 3 Al and Y 3 Al in L1 2( Cu 3 Al ) phase are studied by performing first-principles calculations within the generalized gradient approximation. The calculated lattice constants, static bulk moduli, first-order pressure derivative of bulk moduli and elastic constants for both compounds are reported. The phonon dispersion curves along several high-symmetry lines at the Brillouin zone, together with the corresponding phonon density of states, are determined using the first-principles linear-response approach of the density functional perturbation theory. Temperature variations of specific heat in the range of 0–500 K are obtained using the quasi-harmonic model.

Study of dynamic and thermodynamic properties of zinc-blend and wurtzite cadmium sulfide (CdS) using density functional theory

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Teshome Gerbaba Edossa ◽  
Menberu Mengasha Woldemariam
Keyword(s):  
Density Functional Theory ◽  
Thermodynamic Properties ◽  
Density Functional ◽  
Chemical Potential ◽  
Phonon Dispersion ◽  
Dynamic Properties ◽  
Dielectric Constants ◽  
High Symmetry ◽  
Functional Theory ◽  
Zinc Blend

Abstract The dynamic and thermodynamic properties of wurtzite (wz) and zinc-blend (zb) CdS are investigated within the density functional theory using different approximation methods such as LDA, PBE, and DFT+U. Hellmann–Feynman approach is implemented for the relaxation of atomic position for both phases. To guarantee the accuracy of calculation, the convergence test of total energy with respect to energy cutoff and k-point sampling is performed. The dynamic properties such as phonon dispersion, phonon density of state, frequency along with high symmetry points, static and dynamic polarizability, and dielectric constants are calculated. The obtained values are compared with previous theoretical results. DFT + U approximation gives a good result that is consistent with the available theory. Moreover, the vibrational energy, vibrational free energy, entropy, electron chemical potential, and constant-volume specific heat are obtained within LDA, PBE, and DFT + U approximations.

Theoretical Assessment of the Mechanical, Electronic, and Vibrational Properties of the Paramagnetic Insulating Cerium Dioxide and Investigation of Intrinsic Defects

2014 ◽  
pp. 431-446
Author(s):  
Mohammed Benali Kanoun ◽  
Souraya Goumri-Said
Keyword(s):  
Density Functional ◽  
Phonon Dispersion ◽  
Local Density ◽  
Elastic Stiffness ◽  
Magnetic Impurities ◽  
Generalized Gradient ◽  
Intrinsic Defects ◽  
Local Moments ◽  
Density Functional Perturbation Theory ◽  
Theoretical Assessment

First-principles calculations are performed by taking into account the strong correlation effects on ceria. To obtain an accurate description including f electrons, the authors optimized the Coulomb U parameter for use in Local-Density Approximation (LDA) and Generalized Gradient Approximation (GGA) calculation. A good agreement with experimental data is obtained within the GGA+U (Wu-Cohen scheme). Elastic stiffness constants are found in correct agreement with the available experimental results. Born effective charge, dielectric permittivity, and the phonon-dispersion curves are computed using density functional perturbation theory. The origin of magnetism in undoped ceria with intrinsic defects is investigated. The authors show that both of Ce and O vacancies induce local moments and ferromagnetism without doping ceria by magnetic impurities in this chapter.

THEORETICAL INVESTIGATION OF THE ELASTIC PROPERTIES AND LATTICE DYNAMICS OF THE MgSxSe1-x ALLOY

2007 ◽  
Vol 21 (05) ◽  
pp. 249-259 ◽  
Author(s):  
K. BOUAMAMA ◽  
P. DJEMIA
Keyword(s):  
Elastic Properties ◽  
First Principles ◽  
Lattice Dynamics ◽  
Density Functional ◽  
Local Density ◽  
Lattice Parameter ◽  
First Principles Calculations ◽  
Virtual Crystal Approximation ◽  
Functional Theory ◽  
Density Functional Perturbation Theory

Structural and elastic properties as well as lattice dynamics of ternary MgS x Se 1-x alloy have been studied using first-principles calculations. These are done using density functional theory (DFT) and density functional perturbation theory (DFPT) within the local density approximation (LDA) and employing the virtual-crystal approximation (VCA). We found that the lattice parameter, the elastic constants and the phonon frequencies follow a quadratic law in x.

scholarly journals Electronic and Magnetic Properties of Bulk and Monolayer CrSi2: A First-Principle Study

2018 ◽  
Vol 8 (10) ◽  
pp. 1885 ◽  
Author(s):  
Shaobo Chen ◽  
Ying Chen ◽  
Wanjun Yan ◽  
Shiyun Zhou ◽  
Xinmao Qin ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Density Functional ◽  
Phonon Dispersion ◽  
First Principle ◽  
Metallic Behavior ◽  
Functional Theory ◽  
Phonon Dispersion Curves ◽  
Electronic And Magnetic Properties ◽  
Quantum Size ◽  
Spin Polarized

We investigated the electronic and magnetic properties of bulk and monolayer CrSi2 using first-principle methods based on spin-polarized density functional theory. The phonon dispersion, electronic structures, and magnetism of bulk and monolayer CrSi2 were scientifically studied. Calculated phonon dispersion curves indicated that both bulk and monolayer CrSi2 were structurally stable. Our calculations revealed that bulk CrSi2 was an indirect gap nonmagnetic semiconductor, with 0.376 eV band gap. However, monolayer CrSi2 had metallic and ferromagnetic (FM) characters. Both surface and confinement effects played an important role in the metallic behavior of monolayer CrSi2. In addition, we also calculated the magnetic moment of unit cell of 2D multilayer CrSi2 nanosheets with different layers. The results showed that magnetism of CrSi2 nanosheets was attributed to band energy between layers, quantum size, and surface effects.

scholarly journals The Pseudopotential Approach within Density-Functional Theory: The Case of Atomic Metallic Hydrogen

2020 ◽  
Vol 5 (4) ◽  
pp. 74
Author(s):  
Jin Zhang ◽  
Jeevake Attapattu ◽  
Jeffrey M. McMahon
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Phonon Dispersion ◽  
Metallic Phase ◽  
Metallic Hydrogen ◽  
Spectral Functions ◽  
Functional Theory ◽  
Phonon Dispersion Curves ◽  
Pseudopotential Approach ◽  
Critical Temperature Tc

Internal energies, enthalpies, phonon dispersion curves, and superconductivity of atomic metallic hydrogen are calculated. The standard use of pseudopotentials in density-functional theory are compared with full Coulomb-potential, all-electron linear muffin-tin orbital calculations. Quantitatively similar results are found as far as internal energies are concerned. Larger differences are found for phase-transition pressures; significant enough to affect the phase diagram. Electron–phonon spectral functions α2F(ω) also show significant differences. Against expectation, the estimated superconducting critical-temperature Tc of the first atomic metallic phase I41/amd (Cs-IV) at 500 GPa is actually higher.

Phonons in SiC from INS, IXS, and Ab-Initio Calculations

2006 ◽  
Vol 527-529 ◽  
pp. 689-694 ◽  
Author(s):  
Dieter Strauch ◽  
B. Dorner ◽  
A.A. Ivanov ◽  
M. Krisch ◽  
J. Serrano ◽  
...  
Keyword(s):  
Density Functional ◽  
Phonon Dispersion ◽  
Inelastic Neutron ◽  
First Principles Calculations ◽  
Phonon Dispersion Curves ◽  
Functional Methods ◽  
X Ray Scattering ◽  
Density Functional Perturbation Theory ◽  
Phonon Properties

Preliminary results for the phonon dispersion curves of hexagonal 4H-SiC from experimental inelastic neutron (INS) and X-ray scattering (IXS) are reported and contrasted with those of cubic 3C-SiC and silicon. The experimental frequencies and scattering intensities are in excellent agreement with those from first-principles calculations using density-functional methods. The relative merits of the two experimental techniques and aspects of the density functional perturbation theory and the so-called frozen phonon method for the determination of the basic phonon properties are briefly outlined.

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

2018 ◽  
Vol 73 (11) ◽  
pp. 1025-1035 ◽  
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.

scholarly journals The Case Studies of PtX2 (X = As, P) as High Thermo-power Materials

2021 ◽  
pp. 26-36
Author(s):  
Adewumi I. Popoola ◽  
Adebayo T. Adepoju
Keyword(s):  
Density Functional ◽  
Energy Gap ◽  
Phonon Dispersion ◽  
Material Selection ◽  
Low Frequency ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Density Functional Perturbation Theory ◽  
The Density Functional Theory ◽  
Bending Modes

For thermoelectric applications, semiconductors are generally better than metals and insulators. PtAs2 and PtP2 are indirect energy gap semiconductors that have been predicted with high thermo-powers (PtP2 having higher thermopower than PtAs2). The crystal structure and the electronic structure of PtAs2 and PtP2 are similar except for the energy band gap of PtP2 that is wider than that of PtAs2. The generalized gradient approximation of the Density Functional Theory (DFT), the Density Functional Perturbation Theory (DFPT) were used to explore the full elastic tensors, phonon dispersion and the thermodynamics of PtP2 and PtAs2. This was done to understand the link, if any, between high thermo-power materials and the results. The two compounds are dynamically and elastically stable with higher mechanical properties recorded for PtP2 over PtAs2. The calculated entropy, vibration free energy and the heat capacity at constant volume for PtAs2 (PtP2) were 354.51 (264.18) J/K; -9.21 (27.84) kJ and 276.04 (250.36) J/K at 300 K respectively. The low frequency acoustic modes are between 100 - 170 cm-1 for PtAs2 while it is between100 - 190 cm-1 for PtP2. The calculated high frequency transverse optical (TO) mode for PtP2 is 410 cm-1 while it is 250 cm-1 for PtAs2.  Further analysis of the phonons spectrum showed that additional bond-bending modes can be created in PtP2 than in PtAs2.  All the results points toward PtP2 as better material over PtAs2 for thermoelectric application and these, with or without the knowledge of the energy bandgap can serve to guide material selection/modelling.

Study of the Structural, Dynamic and Thermodynamic Properties of the III- Antimonides Semiconductors

2021 ◽  
Vol 406 ◽  
pp. 250-255
Author(s):  
Sabrina Bounab ◽  
Abdelouahb Bentabet ◽  
Youssef Bouahadda
Keyword(s):  
Thermodynamic Properties ◽  
Density Functional ◽  
Phonon Dispersion ◽  
Local Density ◽  
Harmonic Approximation ◽  
High Symmetry ◽  
Present Contribution ◽  
Structural Dynamic ◽  
Density Functional Perturbation Theory ◽  
Experimental Works

In the present contribution, structural, dynamic, and some thermodynamic properties of the III-Antimonides are studied using the density-functional perturbation theory (DFPT) within the local density approximation (LDA) in combination with the harmonic approximation Our results for the structural properties such as the lattice constant and the bulk modulus were found to agree well with the previous theoretical and experimental works. We have also calculated the phonon dispersion relation, and we found that our phonon calculations show that these compounds are dynamically stable in the zinc blende phase moreover our results of the optical and acoustic phonon frequencies at the high symmetry points Γ, X and L are in good agreement with the available theoretical and experimental data. In addition, the thermodynamic properties, including the free energy, internal energy, entropy, and the heat capacity at constant volume were predicted and discussed.

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