Phases Stability of Ni-Mn-Ga Alloys Studied by Ab Initio Calculations

2014 ◽  
Vol 783-786 ◽  
pp. 1646-1651
Author(s):  
N. Xu ◽  
J.M. Raulot ◽  
Z.B. Li ◽  
Y.D. Zhang ◽  
J. Bai ◽  
...  
Keyword(s):  
Ab Initio ◽  
First Principles ◽  
Density Functional ◽  
Stable Phase ◽  
First Principles Calculations ◽  
Atomic Position ◽  
Functional Theory ◽  
Ab Initio Simulation ◽  
Formation Energies ◽  
Simulation Package

The phase stabilities and magnetic properties in Ni-Mn-Ga alloys are systematically investigated by means of the first-principles calculations within the framework of density functional theory using the vienna ab initio simulation package. The calculated formation energies show that the tetragonal NM martensite is the most stable phase compared with the cubic austenite and the modulated monoclinic martensite for stoichiometric Ni2MnGa. The atomic magnetic moment keeps constant in austenite and NM martensite, whereas those of Ni and Mn in the modulated martensite oscillate according to the atomic position. Furthermore, The formation energies of the various compositions have been systematically calculated.

Systematic first principles calculations of the effects of stacking faults defects on the 4H-SiC band structure

2010 ◽  
Vol 1246 ◽  
Author(s):  
Massimo Camarda ◽  
pietro delugas ◽  
Andrea Canino ◽  
Andrea Severino ◽  
nicolo piluso ◽  
...  
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Stacking Faults ◽  
Perfect Crystal ◽  
First Principles Calculations ◽  
Electronic Band ◽  
Functional Theory ◽  
Experimental Findings ◽  
Electronic Band Structures ◽  
Formation Energies

AbstractShockley-type Stacking faults (SSF) in hexagonal Silicon Carbide polytypes have received considerable attention in recent years since it has been found that these defects are responsible for the degradation of forward I-V characteristics in p-i-n diodes. In order to extend the knowledge on these kind of defects and theoretically support experimental findings (specifically, photoluminescence spectral analysis), we have determined the Kohn-Sham electronic band structures, along the closed path Γ-M-K-Γ, using density functional theory. We have also determined the energies of the SSFs with respect to the perfect crystal finding that the (35) and (44) SSFs have unexpectedly low formation energies, for this reason we could expect these two defects to be easily generated/expanded either during the growth or post-growth process steps.

scholarly journals First-principles calculations of structural and electronics properties of YInN alloy

DYNA ◽  
2021 ◽  
Vol 88 (217) ◽  
pp. 50-57
Author(s):  
Gladys Patricia Abdel Rahim Garzón ◽  
Jairo Arbey Rodriguez Martinez ◽  
María Guadalupe Moreno Armenta ◽  
Miguel Espitia Rico
Keyword(s):  
Phase Transition ◽  
Density Functional Theory ◽  
First Principles ◽  
Density Functional ◽  
Stable Phase ◽  
First Principles Calculations ◽  
Functional Theory ◽  
Technical Data ◽  
Structural And Electronic Properties ◽  
Semiconductor Behavior

We study the structural and electronic properties of YxIn1-xN in the concentrations x = 0, ¼, ½, ¾, and 1 in the B1, B2, B3 and B4 structures using density functional theory (DFT). The calculations show that for Y0.75In0.25N, the B1 structure is the most favorable energetically. It was determined that between  in the  supercell, the most energetically stable structure is the B3 phase. Additionally, between  concentrations x of Yttrium, the compound is most energetically favorable in the B4 phase. Technical data that are in agreement were recently reported by other authors. Finally, between 0.12 , the most stable phase is B1. Additionally, there is no phase transition between the four structures considered. The DOS and band structure show that Y0.75In0.25N in the B1 and B3 phases exhibits semiconductor behavior, with a direct gap of ~0.6 eV and ~0.7 eV, respectively while Y0.75In0.25N in the B4 phase has an indirect one of ~0.8 eV.

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.

scholarly journals Unravelling the Potential of Density Functional Theory through Integrated Computational Environments: Recent Applications of the Vienna Ab Initio Simulation Package in the MedeA® Software

Computation ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 63 ◽  
Author(s):  
Volker Eyert ◽  
Mikael Christensen ◽  
Walter Wolf ◽  
David Reith ◽  
Alexander Mavromaras ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Transition Metal Oxides ◽  
Disordered Systems ◽  
Density Functional ◽  
Industrial Applications ◽  
Functional Theory ◽  
Ab Initio Simulation ◽  
Computer Codes ◽  
Simulation Package

The development of density functional theory and the tremendous increase of compute power in recent decades have created a framework for the incredible success of modern computational materials engineering (CME). CME has been widely adopted in the academic world and is now established as a standard tool for industrial applications. As theory and compute resources have developed, highly efficient computer codes to solve the basic equations have been implemented and successively integrated into comprehensive computational environments leading to unprecedented increases in productivity. The MedeA software of Materials Design combines a set of comprehensive productivity tools with leading computer codes such as the Vienna Ab initio Simulation Package (VASP), LAMMPS, GIBBS and the UNiversal CLuster Expansion code (UNCLE), provides interoperability at different length and time scales. In the present review, technological applications including microelectronic materials, Li-ion batteries, disordered systems, high-throughput applications and transition-metal oxides for electronics applications are described in the context of the development of CME and with reference to the MedeA environment.

Indium in silicon: interactions with native defects and with C impurities

2004 ◽  
Vol 810 ◽  
Author(s):  
P. Alippi ◽  
A. La Magna ◽  
S. Scalese ◽  
V. Privitera
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Electrical Activation ◽  
Thermal Treatments ◽  
Functional Theory ◽  
Ab Initio Simulation ◽  
Native Defects ◽  
Doped Silicon ◽  
Equilibrium Geometries ◽  
Formation Energies

ABSTRACTEquilibrium geometries and formation energies of neutral and charged In complexes with silicon native defects (vacancy (V) and self-interstitials (I)) and with C impurities are investigated within density functional theory, using the Vienna Ab-initio Simulation Package. We determine formation energies and ionization levels of different complexes and discuss the contribution of I and V to indium diffusion. We also identify the In-C defect responsible for the increased electrical activation in In+C-doped silicon samples. The ab initio energetics is then implemented in a continuum diffusion code in order to simulate the diffusion of as-implanted In profiles under different thermal treatments.

REACTIVITY AND STABILITY OF OXYGEN VACANCIES ON TiO2 ANATASE (101) SURFACE: FIRST-PRINCIPLES CALCULATIONS

2011 ◽  
Vol 25 (29) ◽  
pp. 4029-4037
Author(s):  
QILI CHEN ◽  
CHAOQUN TANG ◽  
BO LI ◽  
GUANG ZHENG ◽  
KAIHUA HE
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Oxygen Vacancies ◽  
Atomic Displacement ◽  
Oxygen Adsorption ◽  
First Principles Calculations ◽  
Functional Theory ◽  
Tio2 Anatase ◽  
Technical Parameters ◽  
Formation Energies

In this study, density-functional theory plane-wave pseudopotential method was employed to investigate several oxygen vacancies on TiO 2 anatase (101) surface. At first, a suitable defect-free slab model has been established by analyzing the surface energies and the atomic relaxations influenced by different technical parameters. The formation energies of different kinds of oxygen vacancies in the outermost layer have also been compared as well as the atomic displacement of the defective surfaces. It was found that the presence of bridging oxygen vacancy is more energetically favored and causes larger atomic displacement than other types of surface oxygen vacancies. The reactivity of oxygen vacancies has also been tested by both molecular and dissociated oxygen adsorption. Furthermore, we discussed the configurations and the electronic properties of O 2-adsorbed surface, and found that the appearance of oxygen adsorbate-induced states in the band gap can make the surface sensitive to visible light.

Systematic First Principles Calculations of the Effects of Stacking Fault Defects on the 4H-SiC Band Structure

2010 ◽  
Vol 645-648 ◽  
pp. 283-286 ◽  
Author(s):  
Massimo Camarda ◽  
Pietro Delugas ◽  
Andrea Canino ◽  
Andrea Severino ◽  
Nicolò Piluso ◽  
...  
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Stacking Faults ◽  
Perfect Crystal ◽  
First Principles Calculations ◽  
Electronic Band ◽  
Functional Theory ◽  
Experimental Findings ◽  
Electronic Band Structures ◽  
Formation Energies

Shockley-type Stacking faults (SSF) in hexagonal Silicon Carbide polytypes have received considerable attention in recent years since it has been found that these defects are responsible for the degradation of forward I-V characteristics in p-i-n diodes. In order to extend the knowledge on these kind of defects and theoretically support experimental findings (specifically, photoluminescence spectral analysis), we have determined the Kohn-Sham electronic band structures, along the closed path Γ-M-K-Γ, using density functional theory. We have also determined the energies of the SSFs with respect to the perfect crystal finding that the (35) and (44) SSFs have unexpectedly low formation energies, for this reason we could expect these two defects to be easily generated/expanded either during the growth or post-growth process steps.

Thermodynamic Stability of Hexagonal and Rhombohedral Bn at Cvd Conditions from Van der Waals Corrected First Principles Calculations

2019 ◽  
Author(s):  
Henrik Pedersen ◽  
Björn Alling ◽  
Hans Högberg ◽  
Annop Ektarawong
Keyword(s):  
Thin Films ◽  
Thermodynamic Stability ◽  
First Principles ◽  
Thermal Equilibrium ◽  
Density Functional ◽  
Van Der Waals ◽  
Chemical Vapor ◽  
First Principles Calculations ◽  
Functional Theory ◽  
The Stability

Thin films of boron nitride (BN), particularly the sp<sup>2</sup>-hybridized polytypes hexagonal BN (h-BN) and rhombohedral BN (r-BN) are interesting for several electronic applications given band gaps in the UV. They are typically deposited close to thermal equilibrium by chemical vapor deposition (CVD) at temperatures and pressures in the regions 1400-1800 K and 1000-10000 Pa, respectively. In this letter, we use van der Waals corrected density functional theory and thermodynamic stability calculations to determine the stability of r-BN and compare it to that of h-BN as well as to cubic BN and wurtzitic BN. We find that r-BN is the stable sp<sup>2</sup>-hybridized phase at CVD conditions, while h-BN is metastable. Thus, our calculations suggest that thin films of h-BN must be deposited far from thermal equilibrium.

scholarly journals Hydrogenation and oxidation enhances the thermoelectric performance of Si2BN monolayer

2021 ◽  
Author(s):  
H. R. Mahida ◽  
Deobrat Singh ◽  
Yogesh Sonvane ◽  
Sanjeev K. Gupta ◽  
P. B. Thakor ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Charge Transport ◽  
Transport Properties ◽  
First Principles ◽  
Density Functional ◽  
Thermoelectric Performance ◽  
First Principles Calculations ◽  
Functional Theory

In the present study, we have investigated the structural, electronic, and charge transport properties of pristine, hydrogenated, and oxidized Si2BN monolayers via first-principles calculations based on density functional theory (DFT).

Flexoelectricity in atomic monolayers from first principles

Nanoscale ◽  
2020 ◽  
Author(s):  
Shashikant Kumar ◽  
David Codony ◽  
Irene Arias ◽  
Phanish Suryanarayana
Keyword(s):  
Density Functional Theory ◽  
Transition Metal ◽  
Ab Initio ◽  
First Principles ◽  
Density Functional ◽  
Transition Metal Dichalcogenides ◽  
Functional Theory ◽  
Group Iii ◽  
Flexoelectric Effect ◽  
Metal Dichalcogenides

We study the flexoelectric effect in fifty-four select atomic monolayers using ab initio Density Functional Theory (DFT). Specifically, considering representative materials from each of Group III monochalcogenides, transition metal dichalcogenides...

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