scholarly journals Static and Dynamical Properties of heavy actinide Monopnictides of Lutetium

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Showkat H. Mir ◽  
Prakash C. Jha ◽  
M. S. Islam ◽  
Amitava Banerjee ◽  
Wei Luo ◽  
...  
Keyword(s):  
Density Functional ◽  
Spin Orbit Coupling ◽  
Generalized Gradient ◽  
Salt Crystal ◽  
Functional Theory ◽  
Wave Velocities ◽  
Density Functional Perturbation Theory ◽  
Essential Properties ◽  
Heavy Actinide ◽  
Phonon Properties

Abstract In this work, density functional theory within the framework of generalized gradient approximation has been used to investigate the structural, elastic, mechanical, and phonon properties of lutetium monopnictides in rock-salt crystal structure. The spin orbit coupling and Hubbard-U corrections are included to correctly predict the essential properties of these compounds. The elastic constants, Young’s modulus E, Poisson’s ratio v, shear modulus G, anisotropy factor A and Pugh’s ratio are computed. We found that all lutetium monopnictides are anisotropic and show brittle character. From the wave velocities along [100], [110] and [111] directions, melting temperature of lutetium monopnictides are predicted. Dynamical stability of these monopnictides has been studied by density functional perturbation theory.

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.

First-principles study of BiFeO3 and BaTiO3 in tetragonal structure

2019 ◽  
Vol 33 (21) ◽  
pp. 1950231
Author(s):  
Akbar Ali ◽  
Imad Khan ◽  
Zahid Ali ◽  
Fawad Khan ◽  
Iftikhar Ahmad
Keyword(s):  
Density Functional ◽  
Coupling Effect ◽  
Ferroelectric Materials ◽  
Bandgap Energy ◽  
Spin Orbit Coupling ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Total Energies ◽  
A Site

Structural, electronic, magnetic and mechanical properties of the perovskites BiFeO3 (BFO) and BaTiO3 (BTO) are investigated using density functional theory (DFT). Structural and mechanical parameters are calculated using generalized gradient approximation (GGA) and the results consistent with the available literature. The stable magnetic phases are achieved by optimizing total energies versus volumes of the cells in different magnetic configurations such as nonmagnetic (NM), ferromagnetic (FM) and antiferromagnetic (AFM). BTO is found to be NM while BFO favors G-type AFM (G-AFM) phase. The electronic properties are investigated using GGA, GGA with Hubbard potential (GGA[Formula: see text]+[Formula: see text]U) and modified Becke–Johnson (GGA-mBJ) exchange–correlation functionals. BFO is found to be a direct bandgap semiconductor having gap energy value 3.0 eV whereas BTO is an indirect semiconductor with bandgap energy 2.9 eV. Spin–orbit coupling effect is dominant in BFO due to the larger size of A-site cation. The electrical polarization shows that both the compounds are ferroelectric materials with significant spontaneous polarization of 144.1 [Formula: see text]C/cm2 and 27.9 [Formula: see text]C/cm2 for BFO and BTO respectively.

EXPLORING THE ADIABATIC CONNECTION BETWEEN WEAK- AND STRONG-INTERACTION LIMITS IN DENSITY FUNCTIONAL THEORY

2001 ◽  
Vol 15 (10n11) ◽  
pp. 1672-1683 ◽  
Author(s):  
JOHN P. PERDEW ◽  
STEFAN KURTH ◽  
MICHAEL SEIDL
Keyword(s):  
Perturbation Theory ◽  
Density Functional ◽  
Correlation Energy ◽  
Interaction Strength ◽  
Kcal Mole ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Density Functional Perturbation Theory ◽  
Simple Interaction

If the electron-electron repulsion in an atom or molecule were very weak, it could be treated by orbital-based perturbation theory. If this repulsion were very strong, it could be treated in a model of strict correlation. A simple interaction strength interpolation between these two limits, at fixed electron density, can describe the reality that lies between the extremes. By working entirely within a sophisticated density functional approximation, the meta-generalized gradient approximation, we find that the interpolation error is only about 0.1% for the exchange-correlation energy and about 4 kcal/mole = 0.17 eV for the atomization energy. We also find that real systems probably lie close to the radius of convergence of density functional perturbation theory.

scholarly journals Theoretical calculation for the phonon spectrum and thermodynamic functions of vanadium and its hydride

2021 ◽  
Vol 252 ◽  
pp. 03039
Author(s):  
Qiang Wei-rong ◽  
Wang Xiao-mei ◽  
Liu Wei-qi
Keyword(s):  
Experimental Data ◽  
Density Functional Theory ◽  
Density Functional ◽  
Free Energies ◽  
Generalized Gradient ◽  
Virtual Crystal Approximation ◽  
Functional Theory ◽  
Generalized Gradient Approximation ◽  
Density Functional Perturbation Theory ◽  
Densities Of States

Based on density functional theory(DFT), using virtual crystal approximation and generalized gradient approximation(GGA)with pseudopotential method, the lattices and energies for five crystallines of vanadium hydrides are optimized and calculated. The phonon densities of states are calculated based on density functional perturbation theory(DFPT). The standard Heat capacities, Entropies, Helmholtz free energies and Gibbs functions of vanadium and its hydride are deduced at 298.15K. The calculated results are discussed and compared with experimental data.

scholarly journals Structural and piezoelectric coefficients of AlP under pressure

2018 ◽  
Vol 6 (2) ◽  
pp. 53
Author(s):  
Salah Daoud ◽  
Rabie Mezouar ◽  
Abdelfateh Benmakhlouf
Keyword(s):  
Density Functional ◽  
Structural Parameters ◽  
Generalized Gradient ◽  
Aluminum Phosphide ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Generalized Gradient Approximation ◽  
Zinc Blende ◽  
Density Functional Perturbation Theory ◽  
The Density Functional Theory

The present work aims to investigate the structural parameters and the piezoelectric coefficients of cubic zinc-blende Aluminum phosphide (AlP) under high pressure up to 21 GPa, using plane wave-pseudopotential (PW-PP) approach in the framework of the density functional theory (DFT) and the density functional perturbation theory (DFPT) with the generalized gradient approximation (GGA) for the exchange-correlation functional. The results obtained are analyzed and compared with other data of the literature. The structural parameters and the piezoelectric coefficients calculated here agree well with other data of the literature. We found also that both the direct and converse piezoelectric coefficients increase with increasing pressure up to 21 GPa. 

Structural, optoelectronic and elastic properties of quaternary perovskites CaPd3B4O12 (B = Ti, V)

2019 ◽  
Vol 33 (19) ◽  
pp. 1950212 ◽  
Author(s):  
Shahid Mehmood ◽  
Zahid Ali ◽  
Zainab Hashmi ◽  
Sahar Khan
Keyword(s):  
Density Functional ◽  
Dielectric Material ◽  
Structural Parameters ◽  
Wide Bandgap ◽  
Spin Orbit Coupling ◽  
Hybrid Functional ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Generalized Gradient Approximation ◽  
Reported Data

Perovskites CaPd3B4O[Formula: see text] (B = Ti, V) are studied theoretically using generalized gradient approximation (GGA), GGA-modified Becke–Johnson (GGA-mBJ), GGA with spin-orbit coupling (GGA + SOC) and hybrid functional (HF) in the domain of density functional theory (DFT). The estimated structural parameters are reliable with the experimentally reported data. Cohesive energy and enthalpy show that these compounds are stable thermodynamically. Bonding nature makes known that the chemical bond between Ca/Ti–O is ionic, Pd/V–O is covalent and Ti/V–Ti/V is metallic. The mechanical properties show that these compounds are stable, elastically anisotropic and ductile in nature. CaPd3Ti4O[Formula: see text] is a 2.94 eV direct-wide bandgap semiconductor through GGA-mBJ and consistent with experiments. The optical properties show that CaPd3Ti4O[Formula: see text] is a good dielectric material. The dense electronic states and the wide-gap semiconductor nature of CaPd3Ti4O[Formula: see text] suggest that it can be used as a good thermoelectric material.

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.

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

Open Physics ◽  
2010 ◽  
Vol 8 (5) ◽  
Author(s):  
Katalin Gaál-Nagy
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Local Density ◽  
Vibrational Properties ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Density Functional Perturbation Theory ◽  
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.

scholarly journals Revisiting the Electronic Structures and Phonon Properties of Thermoelectric Antimonide-Tellurides: Spin–Orbit Coupling Induced Gap Opening in ZrSbTe and HfSbTe

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 917
Author(s):  
Souraya Goumri-Said ◽  
Tahani A. Alrebdi ◽  
Engin Deligoz ◽  
Haci Ozisik ◽  
Mohammed Benali Kanoun
Keyword(s):  
Thermoelectric Properties ◽  
Electronic Structures ◽  
Density Functional ◽  
Orbit Coupling ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Functional Theory ◽  
Gap Opening ◽  
Dynamical Properties ◽  
Phonon Properties

We report theoretical studies based on density functional theory within spin-orbit coupling to explore electronic structures, lattice dynamical properties of ZrSbTe and HfSbTe. With spin−orbit coupling included, our findings reveal that ZrSbTe and HfSbTe exhibit a semiconducting behavior with narrow indirect band gaps of 0.10 eV, and 0.15 eV, respectively. Besides, the lattice dynamical properties revealed that the explored materials based on antimonide−tellurides are dynamically stable. On the basis of electronic structures, the thermoelectric properties were computed using the Landauer-Buttiker formula by considering both electron and phonon contributions in the transport properties calculation. We employed Green’s-function method based on the Green-Kubo-Mori formula, where the thermoelectric properties such as the electrical conductivity σ and thermopower α were estimated in terms of the correlation functions. The present work could be viewed as a significant amendment of the electronic nature of ZrSbTe and HfSbTe that were reported to be metallic in literature.

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

SPIN ◽  
2018 ◽  
Vol 08 (04) ◽  
pp. 1850016 ◽  
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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