High-pressure phases ofSiO2using local-density and generalized-gradient approximations

High pressure structural phase transition and electronic properties have been investigated using the linear combination of atomic orbitals (LCAO) method with two exchange-correlation approximations, the generalized gradient approximation (GGA) and local density approximation (LDA). The present study shows phase transitions from B1 to B27 and B27 to B2 at 6.24 GPa and 16.39 GPa, respectively. Lattice constant, bulk modulus, and energy gap of pressure-induced PbSe are found to be in good agreement with previous theoretical and experimental results. Variation of electronic band structure with pressure shows direct band gap along L point of the Brillouin zone.

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First Principles Calculation of the Stability of Iron Bearing Carbonates at High Pressure Conditions

Minerals ◽

10.3390/min10010054 ◽

2020 ◽

Vol 10 (1) ◽

pp. 54

Author(s):

Jun Tsuchiya ◽

Risa Nishida ◽

Taku Tsuchiya

Keyword(s):

High Pressure ◽

High Spin ◽

First Principles ◽

Lower Mantle ◽

Local Density ◽

First Principles Calculation ◽

Generalized Gradient ◽

Carbonate Minerals ◽

Pressure Stability ◽

The Stability

Carbonate minerals such as ferromagnesite (Mg,Fe)CO 3 are suggested to be a possible major deep-carbon host in the lower mantle, because ferromagnesite is possibly stabilized by Fe spin crossover under pressure. However, the behavior of Fe-bearing carbonates under lower mantle pressure conditions has not been suitably examined thus far. Thus, in this study, we investigate the high-pressure stability of ferromagnesite and possible high-pressure structures with the chemical composition of (Mg 0.833 Fe 0.167 )CO 3 via first principles calculation using internally consistent local density approximation with Hubbard parameter (LDA+U) method, which can more accurately account for the electronic state of Fe than the LDA and generalized gradient approximation (GGA) approaches. The enthalpy values obtained via our calculations suggest that (Mg 0.833 Fe 0.167 )CO 3 undergoes phase transition from the R 3 ¯ c structure (high spin) to the P 1 ¯ (high spin) at 50 GPa, and to C2/m (high-spin) structure above 80 GPa, under static 0 K conditions. Therefore, no spin transitions in these carbonate minerals is expected under the lower mantle pressure conditions.

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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.

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

Modern Physics Letters B ◽

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.

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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.

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First-Principles Investigation on Elastic Constants of TiN under High Pressure

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.802.109 ◽

2013 ◽

Vol 802 ◽

pp. 109-113

Author(s):

Kittiya Prasert ◽

Pitiporn Thanomngam ◽

Kanoknan Sarasamak

Keyword(s):

Elastic Constants ◽

First Principles ◽

Local Density ◽

Ambient Pressure ◽

Lattice Parameter ◽

First Principles Calculations ◽

Generalized Gradient ◽

Generalized Gradient Approximation ◽

Shear Distortion ◽

Calculated Lattice Parameter

Elastic constants of NaCl-type TiN under pressure were investigated by first-principles calculations within both local density approximation (LDA) and Perdew-Burke-Ernzerhof generalized-gradient approximation (PBE-GGA). At ambient pressure, the calculated lattice parameter, bulk modulus, and elastic constants of NaCl-type TiN are in well agreement with other available values. Under pressure, all elastic constants,C11,C12, andC44, are found to increase with pressure.C11, which is related to the longitudinal distortion, increases rapidly with pressure whileC12andC44which are related to the transverse and shear distortion, respectively, are much less sensitive to pressure.

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Structural and Electronic Properties of Orthorhombic Phase Bi2Se3 Based On First-Principles Study

Scientific Research Journal ◽

10.24191/srj.v16i2.6359 ◽

2019 ◽

Vol 16 (2) ◽

pp. 77 ◽

Cited By ~ 1

Author(s):

Muhammad Zamir Mohyedin ◽

Afiq Radzwan ◽

Mohammad Fariz Mohamad Taib ◽

Rosnah Zakaria ◽

Nor Kartini Jaafar ◽

...

Keyword(s):

Electronic Properties ◽

First Principles ◽

Density Functional ◽

Local Density ◽

Computer Code ◽

First Principles Calculation ◽

Generalized Gradient ◽

Exchange Correlation ◽

Percentage Difference ◽

Structural And Electronic Properties

Bi2Se3 is one of the promising materials in thermoelectric devices and very useful out of environmental concern due to its efficiency to perform at room temperature. Based on the first-principles calculation of density functional theory (DFT) by using CASTEP computer code, structural and electronic properties of Bi2Se3 were investigated. The calculation is conducted within the exchange-correlation of local density approximation (LDA) and generalized gradient approximation within the revision of Perdew-Burke-Ernzerhof (GGA-PBE) functional. It was found that the results are consistent with previous works of theoretical study with small percentage difference. LDA exchange-correlation functional method is more accurate and have a better agreement than GGA-PBE to describe the structural properties of Bi2Se3 which consist of lattice parameters. LDA functional also shown more accurate electronic structure of Bi2Se3 that consist of band structure and density of states (DOS) which consistent with most previous theoretical works with small percentage difference. This study proves the reliability of CASTEP computer code and show LDA exchange-correlation functional is more accurate in describing the nature of Bi2Se3 compared to the other functionals.

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Structural, electronic and elastic properties of the B2-ScM (M =Au, Hg and Tl) intermetallic compounds: Ab initio calculations

International Journal of Computational Materials Science and Engineering ◽

10.1142/s2047684115500207 ◽

2015 ◽

Vol 04 (04) ◽

pp. 1550020

Author(s):

Ahmad A. Mousa ◽

Jamil M. Khalifeh

Keyword(s):

Mechanical Properties ◽

Bulk Modulus ◽

Intermetallic Compounds ◽

Elastic Constants ◽

Density Functional ◽

Electronic Band Structure ◽

Local Density ◽

Full Potential ◽

Generalized Gradient ◽

Electronic Band

Structural, electronic, elastic and mechanical properties of ScM (M[Formula: see text][Formula: see text][Formula: see text]Au, Hg and Tl) intermetallic compounds are studied using the full potential-linearized augmented plane wave (FP-LAPW) method based on the density functional theory (DFT), within the generalized gradient approximation (GGA) and the local density approximation (LDA) to the exchange-correlation approximation energy as implemented in the Wien2k code. The ground state properties including lattice parameters, bulk modulus and elastic constants were all computed and compared with the available previous theoretical and experimental results. The lattice constant was found to increase in contrast to the bulk modulus which was found to decrease with every substitution of the cation (M) starting from Au till Tl in ScM. Both the electronic band structure and density-of-states (DOS) calculations show that these compounds possess metallic properties. The calculated elastic constants ([Formula: see text], [Formula: see text] and [Formula: see text] confirmed the elastic stability of the ScM compounds in the B2-phase. The mechanical properties and ductile behaviors of these compounds are also predicted based on the calculated elastic constants.

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

Handbook of Research on Nanoscience, Nanotechnology, and Advanced Materials - Advances in Chemical and Materials Engineering ◽

10.4018/978-1-4666-5824-0.ch017 ◽

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.

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