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

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.

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

10.1142/s0217984913502242 ◽

2013 ◽

Vol 27 (30) ◽

pp. 1350224 ◽

Cited By ~ 2

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 ◽

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.

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

10.1142/s0217984915501407 ◽

2015 ◽

Vol 29 (24) ◽

pp. 1550140 ◽

Cited By ~ 3

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 ◽

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.

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

Physical Science International Journal ◽

10.9734/psij/2021/v25i230242 ◽

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 ◽

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

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.406.250 ◽

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 ◽

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.

First-principles investigation of the vibrational properties of 3-tert-butylcyclohexene

Open Physics ◽

10.2478/s11534-009-0167-9 ◽

2010 ◽

Vol 8 (5) ◽

Cited By ~ 1

Author(s):

Katalin Gaál-Nagy

Keyword(s):

First Principles ◽

Density Functional ◽

Local Density ◽

Vibrational Properties ◽

Generalized Gradient ◽

Functional Theory ◽

Exchange Correlation ◽

Characteristic Modes ◽

Correlation Potential

AbstractI present a first-principles investigation of the vibrational properties of the chiral molecule 3-tert-butylcyclohexene. The vibrational density of states (vDOS) of the two existing conformers has been calculated ab initio within the framework of density-functional theory and density-functional perturbation theory, using both the local-density approximation and the generalized-gradient approximation for the exchange-correlation potential. The vDOS of the two conformers are very similar. The vDOS has been investigated with respect to contributions of the cyclohexene ring and the tert-butyl group and also regarding the localization of vibrational modes. Additionally, the eigendisplacements of characteristic modes of 3-tert-butylcyclohexene have been analyzed.

Study of thermo-elastic and lattice dynamics properties of half-Heusler compounds XMgAl (X = Li, Na) by computational investigations

10.1142/s0217984919500933 ◽

2019 ◽

Vol 33 (08) ◽

pp. 1950093 ◽

Cited By ~ 1

Author(s):

A. Afaq ◽

Abu Bakar ◽

M. Rizwan ◽

M. Aftab Fareed ◽

H. Bushra Munir ◽

...

Keyword(s):

Debye Temperature ◽

Elastic Constants ◽

Density Functional ◽

Phonon Dispersion ◽

Dynamic Properties ◽

Mechanical Parameters ◽

Heusler Compounds ◽

Generalized Gradient ◽

Text Type ◽

Quantum Espresso

In this study, thermo-elastic and lattice dynamic properties of XMgAl (X = Li, Na) half-Heusler compounds are investigated using density functional theory implemented in WIEN2k and Quantum ESPRESSO codes. Generalized gradient approximation (GGA) as an exchange correlation function has been used in Kohn–Sham equations. Firstly, the structure of these Heusler compounds is optimized and then these optimized parameters are used to find three elastic constants [Formula: see text], [Formula: see text] and [Formula: see text] for [Formula: see text] type structures. Three elastic constants are then used to determine different elastic moduli like bulk modulus, shear modulus, Young’s modulus and other mechanical parameters like Pugh’s ratio, Poisson’s ratio, anisotropic ratio, sound velocities, Debye temperature and melting temperature. On behalf of these mechanical parameters, the brittle/ductile nature and isotropic/anisotropic behavior of the materials has been studied. Different regions of vibrational modes in the materials are also discussed on behalf of Debye temperature calculations. The vibrational properties of the half-Heusler compounds are computed using Martins–Troullier pseudo potentials implemented in Quantum ESPRESSO. The phonon dispersion curves and phonon density of states in first Brillion zone are obtained and discussed. Reststrahlen band of LiMgAl is found greater than NaMgAl.

First principles calculations of structural, electronic and optical properties of InN compound

International Journal of Modern Physics B ◽

10.1142/s0217979215500289 ◽

2015 ◽

Vol 29 (05) ◽

pp. 1550028 ◽

Cited By ~ 4

Author(s):

R. Graine ◽

R. Chemam ◽

F. Z. Gasmi ◽

R. Nouri ◽

H. Meradji ◽

...

Keyword(s):

Optical Properties ◽

Band Structure ◽

Density Functional ◽

Local Density ◽

Indium Nitride ◽

Alternative Form ◽

Full Potential ◽

Generalized Gradient ◽

Pressure Derivative ◽

Electronic And Optical Properties

We carried out ab initio calculations of structural, electronic and optical properties of Indium nitride ( InN ) compound in both zinc blende and wurtzite phases, using the full-potential linearized augmented plane wave method (FP-LAPW), within the framework of density functional theory (DFT). For the exchange and correlation potential, local density approximation (LDA) and generalized gradient approximation (GGA) were used. Moreover, the alternative form of GGA proposed by Engel and Vosko (EV-GGA) and modified Becke–Johnson schemes (mBJ) were also applied for band structure calculations. Ground state properties such as lattice parameter, bulk modulus and its pressure derivative are calculated. Results obtained for band structure of these compounds have been compared with experimental results as well as other first principle computations. Our results show good agreement with the available data. The calculated band structure shows a direct band gap Γ → Γ. In the optical properties section, several optical quantities are investigated; in particular we have deduced the interband transitions from the imaginary part of the dielectric function.

Structural, elastic and thermodynamic properties of A15-type compounds V3X (X = Ir, Pt and Au) from first-principles calculations

10.1142/s0217984916504145 ◽

2016 ◽

Vol 30 (35) ◽

pp. 1650414 ◽

Cited By ~ 6

Author(s):

Mingliang Wang ◽

Zhe Chen ◽

Dong Chen ◽

Cunjuan Xia ◽

Yi Wu

Keyword(s):

Thermodynamic Properties ◽

Debye Temperature ◽

First Principles ◽

Density Functional ◽

Coefficient Of Thermal Expansion ◽

Local Density ◽

Debye Model ◽

First Principles Calculations ◽

Generalized Gradient ◽

Experimental Values

The structural, elastic and thermodynamic properties of the A15 structure V3Ir, V3Pt and V3Au were studied using first-principles calculations based on the density functional theory (DFT) within generalized gradient approximation (GGA) and local density approximation (LDA) methods. The results have shown that both GGA and LDA methods can process the structural optimization in good agreement with the available experimental parameters in the compounds. Furthermore, the elastic properties and Debye temperatures estimated by LDA method are typically larger than the GGA methods. However, the GGA methods can make better prediction with the experimental values of Debye temperature in V3Ir, V3Pt and V3Au, signifying the precision of the calculating work. Based on the E–V data derived from the GGA method, the variations of the Debye temperature, coefficient of thermal expansion and heat capacity under pressure ranging from 0 GPa to 50 GPa and at temperature ranging from 0 K to 1500 K were obtained and analyzed for all compounds using the quasi-harmonic Debye model.

Density Functional Theory Approach for Muon Sites Estimation in Mn3Sn

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1028.199 ◽

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.