Formation and stability of enhanced superhard nanostructured AlN/VN and AlN/TiN superlattice materials

2002 ◽  
Vol 750 ◽  
Author(s):  
C. Stampfl ◽  
A. J. Freeman
Keyword(s):  
Density Functional ◽  
Interface Energy ◽  
Accurate Estimate ◽  
Full Potential ◽  
Wurtzite Phase ◽  
Functional Theory ◽  
Augmented Plane Wave ◽  
Rocksalt Phase ◽  
Flapw Method ◽  
Linearized Augmented Plane Wave

ABSTRACTUsing density functional theory and the full-potential linearized augmented plane wave (FLAPW) method, we investigate the formation and stability, and atomic structure, of rocksalt AlN/TiN and AlN/VN systems, including properties of the clean surfaces of the constituent materials. Calculations of the adlayer formation energy highlights the effect and interplay of the various energetic contributions on the growth of these strained systems, where the so-called “surface-interface” interaction energy is found to be important for the initial stages of AlN epitaxy. A significant strain energy builds up for increasing number of layers, where it is greater in the AlN/TiN system, which limits the thickness of rocksalt AlN regions that can grow before a structural transition to the lower energy wurtzite phase takes place. From our calculations, together with the known experimental critical thicknesses, we can obtain an accurate estimate of the wurtzite/substrate interface energy. That these values are high explains why the metastable rocksalt phase, which has significantly lower interface energies, is stabilized.

Structural, Electronic, and Magnetic Properties of Surfaces, Interfaces, and Superlattices

1985 ◽  
Vol 63 ◽  
Author(s):  
Arthur J. Freeman ◽  
C. L. Fu ◽  
T. Oguchi
Keyword(s):  
Total Energy ◽  
Density Functional ◽  
Local Density ◽  
Full Potential ◽  
Complex Materials ◽  
Functional Theory ◽  
Augmented Plane Wave ◽  
Local Density Functional Theory ◽  
Flapw Method ◽  
Linearized Augmented Plane Wave

ABSTRACTAdvances in all-electron local density functional theory approaches to complex materials structure and properties made possible by the implementation of new computational/theoretical algorithms on supercomputers are exemplified in our full potential linearized augmented plane wave (FLAPW) method. In this total energy self-consistent approach, high numerical stability and precision (to 10 in the total energy) have been demonstrated in a study of the relaxation and reconstruction of transition metal surfaces. Here we demonstrate the predictive power of this method for describing the structural, magnetic and electronic properties of several systems (surfaces, overlayers, sandwiches, and superlattices).

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.

Structural, Electronic and Elastic Properties of CeTl Intermetallic Compound

2016 ◽  
Vol 28 ◽  
pp. 1-4
Author(s):  
Deepika Shrivastava ◽  
Sankar P. Sanyal
Keyword(s):  
Bulk Modulus ◽  
Elastic Properties ◽  
Density Functional ◽  
Full Potential ◽  
Generalized Gradient ◽  
Pressure Derivative ◽  
Functional Theory ◽  
Augmented Plane Wave ◽  
Cscl Type ◽  
Linearized Augmented Plane Wave

The structural, electronic and elastic properties of CeTl with CsCl-type B2 structure have been investigated using full-potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT) within the generalized gradient approximation (GGA) for exchange and correlation potential. The ground state properties such as lattice constant, bulk modulus and pressure derivative of bulk modulus have been calculated which are in good agreement with available experimental data. The band structure and density of state depict that 4f electrons of Ce element have dominant character in electronic conduction and are responsible for metallic character of CeTl. The charge density plot reveals that the metallic as well as ionic bonding exist between Ce and Tl atoms. The calculated elastic constants indicate that CeTl is mechanically stable in cubic B2 phase and found to be ductile in nature.

Structural and Anisotropic Elastic Properties of Hexagonal YMnO3 in Low Symmetry Determined by First-Principles Calculations

2019 ◽  
Vol 297 ◽  
pp. 120-130 ◽  
Author(s):  
Abdelhakim Chadli ◽  
Mohamed Halit ◽  
Brahim Lagoun ◽  
Ferhat Mohamedi ◽  
Said Maabed ◽  
...  
Keyword(s):  
Density Functional ◽  
Ferromagnetic State ◽  
Hexagonal Structure ◽  
Full Potential ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Augmented Plane Wave ◽  
The Density Functional Theory ◽  
Anisotropic Elastic ◽  
Linearized Augmented Plane Wave

The structural, elastic and anisotropic properties for rare earth manganites compound YMnO3 in ferromagnetic state with hexagonal structure, have been investigated using the ab initio calculations based on the density functional theory, this calculations were based on the full potential linearized augmented plane wave (FP-LAPW) method with the generalized gradient approximation (GGA). The agreement of the DFT (FP-LAPW) calculations including internal atomic relaxations, with the experimental data is very good. Other relevant quantities such as elastic constants, shear modulus, Young’s modulus, Poisson’s ratio, anisotropy factors, sound velocity, and Debye temperature have been calculated and discussed.

Pressure Effect on the Electronic Properties of Cerium Monochalcogenides CeX (X=S, Se, Te) Using Modified Becke-Johnson Exchange Potential and LDA+U

2014 ◽  
Vol 925 ◽  
pp. 390-395
Author(s):  
Noureddine Amrane ◽  
Maamar Benkraouda
Keyword(s):  
Electronic Properties ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Exchange Potential ◽  
Full Potential ◽  
Electronic Band ◽  
Functional Theory ◽  
Augmented Plane Wave ◽  
The Density Functional Theory ◽  
Linearized Augmented Plane Wave

We present a systematic and comparative study of the electronic properties of CeX monochalcogenides, The density of state (DOS) and electronic band structure of CeX (X=S, Se, Te) have been calculated using the full-potential linearized augmented plane-wave (FP-LAPW) + local orbital (lo) method based on the density functional theory (DFT), which is implemented in WIEN2k code. The trends in the high pressure behavior of these systems are discussed. Four approximations for the exchange-correlation functional have been used, the GGA's of Perdew-Burke-Ernzherhof. (PBE08) , Engel-Vosko (EV93), a modified version of the exchange potential proposed by Becke and Johnson (MBJ), and LDA+U is used to calculate the band gaps at different pressures. All methods allow for a description of the Ce f electrons as either localized or delocalized, it is found that the underestimations of the bandgap by means of LDA-GGA and Engel-Vosko are considerably improved by using the modified Becke-Johnson (MBJ) potential for all compounds in the series, On the other hand, LDA+U, method gives good results for the lighter chalcogenides, but it fails to give good results for the heavier cerium monochalcogenides.

Electronic Structure of K2Bi8Se13

2001 ◽  
Vol 691 ◽  
Author(s):  
Daniel I Bilc ◽  
Paul Larson ◽  
S.D. Mahanti ◽  
M.G. Kanatzidis
Keyword(s):  
Density Functional ◽  
Full Potential ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Ordered Structures ◽  
Augmented Plane Wave ◽  
Space Group ◽  
Β Phase ◽  
Indirect Band Gap ◽  
Linearized Augmented Plane Wave

ABSTRACTK2Bi8 Se13 belongs to a class of complex Bi-Te-Se systems which show great potential for thermoelectric performance. This compound forms in two distinct phases α-K2Bi8 Se13 (triclinic with space group P-1) and β-K2Bi8 Se13 (monoclinic with space group P 21/m). In the β-phase, there is substantial disorder at four sites in the unit cell, occupied by two K and two Bi atoms. To understand the electronic properties of these two different phases we have carried out band structure calculations within ab initio density functional theory (DFT) using full potential linearized augmented plane wave (LAPW) method. The generalized gradient approximation (GGA) was used to treat the exchange and correlation potential. Spin-orbit interaction (SOI) was incorporated using a second variational procedure. The α. phase is found to be a semiconductor with an indirect band gap of 0.47eV. For the β-phase we have chosen two different ordered structures. The system is a semi-metal for one of the structures whereas for the other, it is a narrow gap semiconductor with a gap of 0.38eV in the absence of SOI, but the gap collapses and the system becomes a semimetal with low density of states at the Fermi energy when SOI is included.

First-Principles Calculations and the Thermodynamics of Cementite

2010 ◽  
Vol 638-642 ◽  
pp. 3319-3324 ◽  
Author(s):  
Jae Hoon Jang ◽  
In Gee Kim ◽  
H.K.D.H. Bhadeshia
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Full Potential ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Augmented Plane Wave ◽  
Plane Wave Method ◽  
Lattice Constants ◽  
Unit Cells ◽  
Linearized Augmented Plane Wave

Thermodynamic data for the substitution of silicon and manganese in cementite have been estimated using first-principles methods in order to aid the design of steels where it is necessary to control the precipitation of this phase. The need for the calculations arises from the fact that for silicon the data cannot be measured experimentally; manganese is included in the analysis to allow a comparison with its known behaviour. The calculations for Fe3C, (Fe11Si4c)C4, (Fe11Si8d)C4, (Fe11Mn4c)C4 and (Fe11Mn8d)C4 are based on the total energy all-electron full-potential linearized augmented plane-wave method within the generalized gradient approximation to density functional theory. The output includes the ground state lattice constants, atomic positions and bulk moduli. It is found that (Fe11Si4c)C4 and (Fe11Si8d)C4 have about 52 and 37 kJ greater formation energy when compared with a mole of unit cells of pure cementite, whereas the corresponding energy for (Fe11Mn4c)C4 and (Fe11Mn8d)C4 is less by about 5 kJ mol1. These results for manganese match closely with published trends and data; a similar comparison is not possible for silicon but we correctly predict that the solubility in cementite should be minimal.

The mechanical, optical and thermoelectric properties of MCoF3 (M = K and Rb) compounds

2017 ◽  
Vol 31 (06) ◽  
pp. 1750033 ◽  
Author(s):  
A. A. Mubarak
Keyword(s):  
Thermoelectric Properties ◽  
Density Functional ◽  
Full Potential ◽  
Functional Theory ◽  
Half Metallic ◽  
Augmented Plane Wave ◽  
The Density Functional Theory ◽  
Type Character ◽  
P Type ◽  
Linearized Augmented Plane Wave

This is an ab initio study instituted on the density functional theory (DFT) and the full-potential linearized augmented plane wave (FP-LAPW) calculations that are performed to analyze the mechanical, electronic, optical and thermoelectric properties of the cubic MCoF3 compound (M = K and Rb). The studied compounds are found thermodynamically and mechanically stable. Moreover, these compounds are found to be elastically anisotropic and ductile. KCoF3 and RbCoF3 are classified as half-metallic and anti-ferromagnetic compounds. The optical properties are investigated from the dielectric function for the different energy ranges. The thermoelectric properties such as transport properties are determined as a function of temperature using BoltzTrape code in the range of 20–800 K. The present compounds are found to have p-type character. Also, the majority charge carriers are found to be electrons rather than hole. Useful mechanical, spintronic, optical and thermoelectric applications are predicted based upon the calculations.

scholarly journals The study of structural, elastic, electronic and optical properties of CsYx I(1 − x)(Y = F, Cl, Br) using density functional theory

2017 ◽  
Vol 35 (1) ◽  
pp. 197-210 ◽  
Author(s):  
Shabeer Ahmad Mian ◽  
Muhammad Muzammil ◽  
Gul Rahman ◽  
Ejaz Ahmed
Keyword(s):  
Optical Properties ◽  
Density Functional ◽  
Full Potential ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Augmented Plane Wave ◽  
Generalized Gradient Approximation ◽  
G Ratio ◽  
Linearized Augmented Plane Wave ◽  
Incremental Addition

AbstractThe structural, electronic, elastic and optical properties of CsYx I(1 − x)(Y = F, Cl, Br) are investigated using full potential linearized augmented plane wave (FP-LAPW) method within the generalized gradient approximation (GGA). The ground state properties such as lattice constant (ao) and bulk modulus (K) have been calculated. The mechanical properties including Poisson’s ratio (σ), Young’s modulus (E), anisotropy factor (A) and shear modulus (G) were also calculated. The results of these calculations are comparable with the reported experimental and theoretical values. The ductility of CsYx I(1 − x) was analyzed using Pugh’s rule (B/G ratio) and Cauchy’s pressure (C12−C44). Our results revealed that CsF is the most ductile among the CsYxI(1 − x)(Y = F, Cl, Br) compounds. The incremental addition of lighter halogens (Yx) slightly weakens the strength of ionic bond in CsYxI(1 − x). Moreover, the optical transitions were found to be direct for binary and ternary CsYxI(1 − x). We hope that this study will be helpful in designing binary and ternary Cs halides for optoelectronic applications.

First Principle Investigation of Structural, Electronic and Optical Properties of Quaternary BxInyGa1−x−yN Compounds

SPIN ◽  
2020 ◽  
Vol 10 (04) ◽  
pp. 2050024 ◽  
Author(s):  
M’hamed Larbi ◽  
Ali Bentouaf ◽  
Abdelkader Bouazza ◽  
Bouharkat Mbarek ◽  
Brahim Aïssa
Keyword(s):  
Density Functional ◽  
Nonlinear Dependence ◽  
Full Potential ◽  
Quaternary Alloys ◽  
Functional Theory ◽  
Augmented Plane Wave ◽  
Plane Wave Method ◽  
Zinc Blende ◽  
Augmented Plane Wave Method ◽  
Linearized Augmented Plane Wave

We report on our results obtained on the physical properties of BxInyGa[Formula: see text]N quaternary alloys in the zinc-blende phase that are thoroughly considered by the linearized augmented plane wave method, with a full potential within density functional theory, for different concentrations [Formula: see text] and [Formula: see text] as employed in the Wien2k code. We calculated the structural properties, including lattice constant [Formula: see text] and the bulk modulus [Formula: see text]. We computed as well the band structures, the dielectric constant and the refractive index of our quaternary alloys compounds. Finally, nonlinear dependence on the compositions [Formula: see text] and [Formula: see text] are investigated in-depth and still expecting for experimental confirmations. To the best of our knowledge, this is the first theoretical investigation of BxInyGa[Formula: see text]N alloy conducted to date.

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