scholarly journals Magnetic Collapse and the Behavior of Transition Metal Oxides: FeO at High Pressures

1997 ◽  
Vol 499 ◽  
Author(s):  
R. E. Cohen ◽  
Y. Fei ◽  
R. Downs ◽  
I. I. Mazin ◽  
D. G. Isaak
Keyword(s):  
Transition Metal Oxides ◽  
High Pressures ◽  
Local Density ◽  
Hexagonal Phase ◽  
Spin Transition ◽  
Generalized Gradient ◽  
Augmented Plane Wave ◽  
First Order ◽  
First Order Transition ◽  
Linearized Augmented Plane Wave

ABSTRACTLinearized augmented plane wave (LAPW) results are presented for FeO at high pressures using the Generalized Gradient Approximation (GGA) to study the high-spin low-spin transition previously predicted by LAPW with the Local Density Approximation (LDA) and Linear Muffin Tin Orbital (LMTO-ASA) methods within the GGA. We find a first-order transition at a pressure of about 105 GPa for the cubic lattice, consistent with earlier LAPW results, but much lower than obtained with the LMTO. The results are generally consistent with recent Mössbauer experiments that show a transition at about 100 GPa. We also discuss the origin of the transition, and show that it is not due to electrostatic crystal-field effects, but is rather due to hybridization and band widening with pressure. Examination of experimental data and computations suggest that the high pressure hexagonal phase of FeO is likely a polytype between the B8 NiAs and anti-B8 AsNi structures. The former is predicted to be an antiferromagnetic metal, and the latter an antiferromagnetic insulator. Implications for geophysics are discussed.

Ab initio studies of the structural, electronic, and optical properties of quaternary BxAlyGa1–x–yN compounds

2016 ◽  
Vol 71 (2) ◽  
pp. 125-134 ◽  
Author(s):  
M’hamed Larbi ◽  
Rabah Riane ◽  
Samir F. Matar ◽  
Ahmed Abdiche ◽  
Mustapha Djermouni ◽  
...  
Keyword(s):  
Bulk Modulus ◽  
Local Density ◽  
Lattice Parameter ◽  
Band Gaps ◽  
Full Potential ◽  
Generalized Gradient ◽  
Augmented Plane Wave ◽  
Plane Wave Method ◽  
Structural And Electronic Properties ◽  
Linearized Augmented Plane Wave

AbstractOriginal first-principles calculations were performed to study the structural and electronic properties of quaternary BxAlyGa1–x–yN compounds, using the non-relativistic full-potential linearized augmented plane wave method as employed in the Wien2k code. For the exchange-correlation potential, local density approximation and generalized gradient approximation have been used to calculate theoretical lattice parameters, bulk modulus, and their pressure derivatives. Non-linear variation with compositions x and y of the lattice parameter, bulk modulus, and direct and indirect band gaps have been found. The calculated bowing of the fundamental band gaps is in good agreement with the available experimental and theoretical values.

scholarly journals Модельный подход к описанию свойств графана: аналитические результаты

2020 ◽  
Vol 62 (12) ◽  
pp. 2188
Author(s):  
С.Ю. Давыдов
Keyword(s):  
Mechanical Properties ◽  
Local Density ◽  
Hexagonal Structure ◽  
Full Potential ◽  
Dirac Cone ◽  
Generalized Gradient ◽  
Augmented Plane Wave ◽  
Experimental Works ◽  
Linearized Augmented Plane Wave ◽  
Good Agreement

Since its discovery in 2004, graphene has attracted the intention of several researchers in the world because of its fascinating electronic and mechanical properties. Various theoretical and experimental works have been devoted to this material. In this paper, we used a full-potential linearized augmented plane-wave (FP-LAPW) method to investigate the structural, electronic, and mechanical properties of graphene in hexagonal structure within local density and generalized gradient approximations (LDA and GGA). Our results are found in good agreement with other theoretical and experimental contributions. Using a modified Becke--Johnsone GGA approximation, we have also confirmed that graphene is a zero-gap semiconductor with the presence of a Dirac cone. In our contribution, we have also calculated the elastic constants, the Young's modulus and Poisson's ratio of graphene that are found in good agreement with the results published in the literature.

Ideal Tensile Strength of Ni3Al and Fe3Al with D03 Structure

2007 ◽  
Vol 567-568 ◽  
pp. 77-80 ◽  
Author(s):  
Dominik Legut ◽  
Mojmír Šob
Keyword(s):  
Tensile Strength ◽  
Density Functional ◽  
Local Density ◽  
Magnetic Moments ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Augmented Plane Wave ◽  
Plane Wave Method ◽  
The Density Functional Theory ◽  
Linearized Augmented Plane Wave

The ideal tensile strength along the [111] direction in the Fe3Al and Ni3Al intermetallic compounds with the D03 structure has been calculated from the first principles using the fullpotential linearized augmented plane-wave method (FP LAPW) within the density functional theory (DFT). The strains corresponding to the maximum sustainable stresses in both materials were determined and compared. The behavior of atomic magnetic moments as a function of strain was analyzed. The tensile test simulations have been theoretically simulated employing both the local density approximation (LDA) and generalized gradient approximation (GGA) for the exchangecorrelation potential.

scholarly journals Structural, electronic, optical properties and first-principles calculations of Sr1-xCaxWO4 ceramics

2019 ◽  
Vol 9 (3) ◽  
pp. 199-211
Author(s):  
Mohammed Ait Haddouch ◽  
Youssef Tamraoui ◽  
Fatima-Ezzahra Mirinioui ◽  
Youssef Aharbil ◽  
Hicham Labrim ◽  
...  
Keyword(s):  
Optical Properties ◽  
Density Functional ◽  
Local Density ◽  
Solid State Reaction Method ◽  
Full Potential ◽  
X Ray Diffraction ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Augmented Plane Wave ◽  
Linearized Augmented Plane Wave

A series of strontium calcium tungstates Sr1-xCaxWO4 powders with (x = 0; 0.25; 0.5; 0.75 and 1.0) were prepared by solid-state reaction method and analyzed by X-ray diffraction (XRD). All these compositions possess a tetragonal scheelite structure with I41/a space group. Raman active vibrational modes in the range from 20 to 1000 cm-1 of the series Sr1-xCaxWO4 with tetragonal structure exhibit 13 modes in arrangement with the Group theory analysis of structural Raman-active modes. The optical properties were investigated using the diffuse reflectance UV–visible absorbance spectrum. Based on Density Functional Theory (DFT) and using full Potential-linearized Augmented Plane Wave (FP-LAPW) method with the Local Density Approximation and the Generalized Gradient Approximation (GGA), implemented in the Wien2k package, we have investigated electronic and optical properties of all the compositions. The results indicate a decrease in the values of the optical direct bandgap (from 4.29 to 3.87 eV) with the increase of Ca into SrWO4 lattice, which is in good agreement with our experimental results.

Modified Becke-Johnson Approach for Governing Half Metallic Ferromagnetism in Cr-Doped GaP DMS Compound

2012 ◽  
Vol 585 ◽  
pp. 265-269
Author(s):  
Hardev S. Saini ◽  
Mukhtiyar Singh ◽  
Manish K. Kashyap
Keyword(s):  
Spin Exchange ◽  
Local Density ◽  
Magnetic Semiconductor ◽  
Full Potential ◽  
Generalized Gradient ◽  
Half Metallic ◽  
Augmented Plane Wave ◽  
Linearized Augmented Plane Wave ◽  
Metallic Ferromagnetism ◽  
Half Metallic Ferromagnetism

The electronic and magnetic properties of Ga1-xCrxP Dilute Magnetic Semiconductor (DMS) compound at doping concentration, x = 0.125 has been calculated using full potential linearized augmented plane wave (FPLAPW) method. The exchange and correlation (XC) effects are taken into account by a semi local, orbital independent modified Becke-Johnson (mBJ) potential as coupled with Local Density Approximation (LDA). Our calculation shows that Cr induces the ferromagnetism in this compound and there is large half metallic (HM) gap appearing in the minority spin channel. We observed that mBJLDA potential enhances the HM gap by ~ 0.25 eV as compared to from its value in Generalized Gradient Approximation (GGA). The improved HM gap can be understood in terms of the mBJLDA-enhanced spin exchange splitting.

Density Functional Theory Approach for Muon Sites Estimation in Mn3Sn

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.

THE FIRST PRINCIPLE STUDY OF COMPARISON OF DIVALENT AND TRIVALENT IMPURITY IN RRAM DEVICES USING GGA+U

2021 ◽  
pp. 2150039
Author(s):  
EJAZ AHMAD KHERA ◽  
HAFEEZ ULLAH ◽  
MUHAMMAD IMRAN ◽  
HASSAN ALGADI ◽  
FAYYAZ HUSSAIN ◽  
...  
Keyword(s):  
Data Storage ◽  
Random Access ◽  
Resistive Random Access Memory ◽  
Full Potential ◽  
Generalized Gradient ◽  
Augmented Plane Wave ◽  
Generalized Gradient Approximation ◽  
Metal Insulator Metal ◽  
Structure Density ◽  
Linearized Augmented Plane Wave

Resistive switching (RS) performances had prodigious attention due to their auspicious potential for data storage. Oxide-based devices with metal insulator metal (MIM) structure are more valuable for RS applications. In this study, we have studied the effect of divalent (nickel) as well as trivalent (aluminum) dopant without and with oxygen vacancy (V[Formula: see text] in hafnia (HfO[Formula: see text]-based resistive random-access memory (RRAM) devices. All calculations are carried out within the full potential linearized augmented plane-wave (FP-LAPW) method based on the WIEN2k code by using generalized gradient approximation (GGA) and generalized gradient approximation with U Hubbard parameters (GGA+U) approach. The studies of the band structure, density of states and charge density reveal that HfNiO2+Vo are more appropriate dopant to enhance the conductivity for RRAM devices.

Ab-initio thermodynamic and elastic properties of AlNi and AlNi3 intermetallic compounds

2018 ◽  
Vol 32 (11) ◽  
pp. 1850129 ◽  
Author(s):  
Shahram Yalameha ◽  
Aminollah Vaez
Keyword(s):  
Intermetallic Compounds ◽  
Elastic Properties ◽  
Density Functional ◽  
Full Potential ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Augmented Plane Wave ◽  
Wide Range ◽  
Computational Data ◽  
Linearized Augmented Plane Wave

In this paper, thermodynamic and elastic properties of the AlNi and AlNi3 were investigated using density functional theory (DFT). The full-potential linearized augmented plane-wave (APW) in the framework of the generalized gradient approximation as used as implemented in the Wien2k package. The temperature dependence of thermal expansion coefficient, bulk modulus and heat capacity in a wide range of temperature (0–1600 K) were investigated. The calculated elastic properties of the compounds show that both intermetallic compounds of AlNi and AlNi3 have surprisingly negative Poisson’s ratio (NPR). The results were compared with other experimental and computational data.

ELASTIC, ELECTRONIC AND THERMODYNAMIC PROPERTIES OF Rh3X(X = Zr, Nb and Ta) INTERMETALLIC COMPOUNDS

2014 ◽  
Vol 28 (03) ◽  
pp. 1450006 ◽  
Author(s):  
M. OULD KADA ◽  
T. SEDDIK ◽  
A. SAYEDE ◽  
R. KHENATA ◽  
A. BOUHEMADOU ◽  
...  
Keyword(s):  
Thermodynamic Properties ◽  
Intermetallic Compounds ◽  
Density Functional ◽  
High Pressures ◽  
Local Density ◽  
Generalized Gradient ◽  
Charge Densities ◽  
Densities Of States ◽  
Bonding Properties ◽  
Experimental Values

Structural, electronic, elastic and thermodynamic properties of Rh 3 X ( X = Zr , Nb , Ta ) intermetallic compounds are investigated in the framework of density functional theory (DFT). The exchange-correlation (XC) potential is treated with the generalized gradient approximation (GGA) and local density approximation (LDA). The computed ground state properties agree well with the available theoretical and experimental values. The elastic constants are obtained by calculating the total energy versus volume conserving strains using Mehl model. The electronic and bonding properties are discussed from the calculations of band structures (BSs), densities of states and electron charge densities. The volume and bulk modulus at high pressure and temperature are investigated. Additionally, thermodynamic properties such as the heat capacity, thermal expansion and Debye temperature at high pressures and temperatures are also analyzed.

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