First-principles study of structural, electronic, elastic and phonon properties of AB2O4(A = Ge,Si;B = Mg,Zn,Cd) spinel oxides

2016 ◽  
Vol 30 (03) ◽  
pp. 1650002 ◽  
Author(s):  
Abdullah Candan ◽  
Gökay Uğur
Keyword(s):  
Density Functional ◽  
Phonon Dispersion ◽  
Direct Method ◽  
Structural Parameters ◽  
Functional Theory ◽  
Phonon Dispersion Curves ◽  
Phonon Spectra ◽  
Predicted Values ◽  
First Time ◽  
Phonon Properties

The structural, electronic, elastic and phonon properties of the cubic spinels AB2O4 (A = Ge, Si; B = Mg, Zn, Cd) compounds at zero pressure are investigated via density functional theory (DFT) using the Perdew–Burke–Ernzerhof (PBE) exchange–correlation functional. It has been shown that the predicted values of the structural parameters ([Formula: see text] and [Formula: see text]), bulk modulus [Formula: see text], elastic constants [Formula: see text], shear modulus [Formula: see text] and [Formula: see text] ratio are in good agreement with the previously reported results. The phonon dispersion curves of the AB2O4 (A = Ge, Si; B = Mg, Zn, Cd) are calculated for the first time using the direct method. The estimated phonon spectra indicate that GeMg2O4, GeZn2O4, GeCd2O4, SiMg2O4 and SiZn2O4 are dynamically stable in the cubic spinel structure.

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.

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.

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.

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.

scholarly journals Cтруктура и динамика решетки кристаллов Nd-=SUB=-2-=/SUB=-TiO-=SUB=-5-=/SUB=- и Sm-=SUB=-2-=/SUB=-TiO-=SUB=-5-=/SUB=-: ab initio расчет

2019 ◽  
Vol 61 (6) ◽  
pp. 1151
Author(s):  
В.А. Чернышев ◽  
В.С. Рюмшин
Keyword(s):  
Crystal Structure ◽  
Density Functional ◽  
Vibration Frequencies ◽  
Hybrid Functional ◽  
Fundamental Vibration ◽  
Functional Theory ◽  
Lattice Constants ◽  
Hartree Fock ◽  
Phonon Spectra ◽  
First Time

Crystal structure and phonon spectra R2TiO5 (R = Nd, Sm) were studied within the framework of density functional theory and MO LKAO approach. The calculations were performed by using hybrid functional that takes into account both local and nonlocal (at the Hartree-Fock formalism) exchange. The coordinates of the ions in the unit cell and the lattice constants are calculated. The fundamental vibration frequencies of R2TiO5 (R = Nd, Sm) were calculated. The relative intensities of the Raman lines and the intensity of the IR-active modes have been calculated. The elastic constants of the crystal have been calculated at the first time.

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.

scholarly journals Vibrational Properties and DFT Calculations of Perovskite-Type Methylhydrazinium Manganese Hypophosphite

Molecules ◽  
2020 ◽  
Vol 25 (21) ◽  
pp. 5215
Author(s):  
Aneta Ciupa-Litwa ◽  
Maciej Ptak ◽  
Edyta Kucharska ◽  
Jerzy Hanuza ◽  
Mirosław Mączka
Keyword(s):  
Dft Calculations ◽  
Density Functional ◽  
Functional Materials ◽  
Polycrystalline Sample ◽  
Vibrational Modes ◽  
Functional Theory ◽  
Polarized Raman ◽  
First Time ◽  
Perovskite Type ◽  
Phonon Properties

Recently discovered hybrid perovskites based on hypophosphite ligands are a promising class of compounds exhibiting unusual structural properties and providing opportunities for construction of novel functional materials. Here, we report for the first time the detailed studies of phonon properties of manganese hypophosphite templated with methylhydrazinium cations ([CH3NH2NH2][Mn(H2PO2)3]). Its room temperature vibrational spectra were recorded for both polycrystalline sample and a single crystal. The proposed assignment based on Density Functional Theory (DFT) calculations of the observed vibrational modes is also presented. It is worth noting this is first report on polarized Raman measurements in this class of hybrid perovskites.

scholarly journals Structural Optimization and the Study of the Electronic, Mechanical, Thermodynamic and Phonon Properties of Mg2sn from First Principle

2020 ◽  
pp. 60-71
Author(s):  
I. S. Okunzuwa ◽  
E. Aigbekaen, Eddy ◽  
T. Philips Chidubem
Keyword(s):  
Density Functional ◽  
Phonon Dispersion ◽  
Young Modulus ◽  
Computer Code ◽  
Pressure Derivative ◽  
Functional Theory ◽  
Optical Branch ◽  
Cauchy Pressure ◽  
Phonon Properties ◽  
Good Agreement

First principles pseudopotential method based on density functional theory is used to investigate the Structural, Mechanical, Phonon, Thermodynamic and Electronic properties of Mg2Sn. The equilibrium properties including lattice constant, bulk modulus, pressure derivative cohesive energy, young modulus, shear modulus were determined. The results obtained were compared with available experimental and other available results. Mg2Sn was found to be brittle in nature with a non-metallic properties as shown by the value of the Cauchy pressure of -4.03. The Phonon dispersion curve of Mg2Sn was obtained utilizing the PBE-GGA exchange-correlation potential as employed in the Vienna Ab-Initio Simulation Package (VASP) computer code. The gap separating the acoustic and the optical branch of the curve was found to be about 50cm-1 at X-point. The thermodynamic properties of the material was investigated in the temperature of 0-800K. At room temperature, the calculated value of the specific heat capacity ( ) is 71.28J/mol which is in good agreement with experimental and other results. Mg2Sn was found to a narrow gap semiconductor with an indirect bandgap of magnitude of 0.175eV.

scholarly journals Basic Elastic Properties Predictions of Cubic Cerium Oxide Using First-Principles Methods

2013 ◽  
Vol 2013 ◽  
pp. 1-4 ◽  
Author(s):  
Jon C. Goldsby
Keyword(s):  
Cerium Oxide ◽  
Density Functional ◽  
Nearest Neighbor ◽  
Energy Gap ◽  
Phonon Dispersion ◽  
Electronic Devices ◽  
Functional Theory ◽  
Phonon Dispersion Curves ◽  
Conduction Bands ◽  
Elastic Responses

Computational material methods were used to predict and investigate electrical and structural properties of cerium oxide (CeO2). Density functional theory was used to obtain the optimized crystal structure and simulate the material’s electronic and elastic responses. Oxygen to oxygen nearest neighbor distance is 2.628 Å, while oxygen to cerium distance is calculated to be 2.276 Å. The conduction band has a prominent set of bands, which exists between 6 and 17 eV. An indirect energy gap (6.04 eV) exists between the valence and conduction bands. The independent elastic constants allow a mechanical assessment on the suitability of cubic cerium oxide as a substrate for advanced electronic devices. The calculated results of phonon dispersion curves are also given.

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