Elastic Constants and Related Properties of the Group III-Nitrides

1995 ◽  
Vol 395 ◽  
Author(s):  
Kwiseon Kim ◽  
Walter R. L. Lambrecht ◽  
B. Segall
Keyword(s):  
Elastic Constants ◽  
First Principles ◽  
Bond Angle ◽  
Local Density ◽  
Group Iii Nitrides ◽  
Internal Displacement ◽  
Orbital Method ◽  
Model Parameters ◽  
Full Potential ◽  
Group Iii

ABSTRACTThe elastic constants of the Group-III nitrides, c-BN, AlN and GaN were calculated from first-principles using the full-potential linear muffin-tin orbital method and local density approximation. The relation between the elatic constants in zincblende and wurtzite is studied by means of a tensor coordinate transformation approach. The latter combined with a correction for the internal displacement of the rotated tetrahedra is found to provide good results for the Ch11Ch12 and Ch44 but not for Ch13 and Ch33. These two require explicit calculations involving distortions along the c-axis. The calculations also provide information on the transverse optical phonons. By deriving Keating model parameters we show that BN is much stiffer against bond-angle distortions than the other nitrides.

FIRST-PRINCIPLES HIGH-PRESSURE ELASTIC AND THERMODYNAMIC PROPERTIES OF TANTALUM

2011 ◽  
Vol 25 (10) ◽  
pp. 1393-1407 ◽  
Author(s):  
JING-HE WU ◽  
XIAN-LIN ZHAO ◽  
YOU-LIN SONG ◽  
GUO-DONG WU
Keyword(s):  
Thermodynamic Properties ◽  
Elastic Constants ◽  
First Principles ◽  
Equations Of State ◽  
Debye Model ◽  
Thermal Expansivity ◽  
Orbital Method ◽  
Full Potential ◽  
Body Centered Cubic ◽  
Theoretical Results

The all-electron full-potential linearized muffin-tin orbital method, by means of quasi-harmonic Debye model, is applied to investigate the elastic constant and thermodynamic properties of body-centered-cubic tantalum (bcc Ta). The calculated elastic constants of bcc Ta at 0 K is consistent with the previous experimental and theoretical results. Our calculations give the correct trends for the pressure dependence of elastic constants. By using the convenient quasi-harmonic Debye model, we refined the thermal equations of state. The thermal expansivity and some other thermal properties agree well with the previous experimental and theoretical results.

First principles calculation of the elastic constants of intermetallic compounds: metastable Al3Li

1991 ◽  
Vol 6 (2) ◽  
pp. 324-329 ◽  
Author(s):  
X-Q. Guo ◽  
R. Podloucky ◽  
A.J. Freeman
Keyword(s):  
Young’S Modulus ◽  
Elastic Constants ◽  
First Principles ◽  
Local Density ◽  
Young's Modulus ◽  
Poisson Ratio ◽  
First Principles Calculation ◽  
Full Potential ◽  
A Value ◽  
Experimental Values

We report first principles local density calculations for the metastable Al3Li intermetallic compound with cubic L12 crystal structure using the full-potential linearized augmented plane wave method. From the second derivative of the total energy as a function of volume, and generated tetragonal and trigonal lattice distortions, the elastic constants C11, C12, and C44 were derived yielding C11 = 158 GPa, C12 = 29.4 GPa, and C44 = 57.7 GPa. Because of the very high Young's modulus (E = 141 GPa) compared, for example, to pure Al (E = 66 GPa), it is suggested that Al3Li plays an important role in strengthening the Al–Li alloys. The calculated Young's modulus appears in good agreement with experimental estimates when the experimental values are extrapolated to 0 K. Although the Young's modulus of Al3Li is increased in comparison to Al, the calculated bulk modulus is decreased to a value of 72 GPa as compared to pure Al (82 GPa), in agreement with experiment. As a result, the Poisson ratio is reduced to ŝ = 0.173 as compared to the value 1/3 for an isotropic medium. Because of this and the high Young's modulus, the calculated Debye temperature ΘD at 0 K amounts to 672 K, which is substantially larger than ΘD for Al, which is about 400 K.

scholarly journals First-principles calculations to investigate structural, electronic and optical properties of (AlSb)m/(GaSb)n superlattices

2020 ◽  
Vol 38 (2) ◽  
pp. 320-327
Author(s):  
M. Caid ◽  
D. Rached
Keyword(s):  
Optical Properties ◽  
First Principles ◽  
Density Functional ◽  
Local Density ◽  
Orbital Method ◽  
Full Potential ◽  
Functional Theory ◽  
Electronic And Optical Properties ◽  
The Density Functional Theory ◽  
Direct Band

AbstractThe structural, electronic and optical properties of (AlSb)m/(GaSb)n (m-n: 1-1, 2-2, 1-3 and 3-1) superlattices are investigated within the density functional theory (DFT) by using the last version of the first principles full potential linear muffin tin orbital method (FP-LMTO) as implemented in LmtART 7.0 code. The exchange and correlation potential is treated by the local density approximation (LDA) for the total energy calculations. Our calculations of the band structure show that the superlattices (n ≠ 1) have a direct band gap Γ-Γ. The optical constants, including the dielectric function ϵ(w), the refractive index n(w) and the reflectivity R(w) are calculated and discussed.

Equilibrium Structure and Schottky Barriers at Eras/Gaas Interfaces

1997 ◽  
Vol 492 ◽  
Author(s):  
A. G. Petukhov ◽  
B. T. Hemmelman ◽  
W. R. L. Lambrecht
Keyword(s):  
Local Density ◽  
Equilibrium Structure ◽  
Schottky Barriers ◽  
Orbital Method ◽  
Full Potential ◽  
Face Centered Cubic ◽  
Erbium Arsenide ◽  
Self Energy ◽  
Ideal Situation ◽  
Face Centered

ABSTRACTThe equilibrium structures as well as the electronic Schottky barriers for (100) Erbium-Arsenide/Gallium-Arsenide (ErAs/GaAs) arsenic and gallium terminated interfaces have been determined by ab-initio calculations using the local-density approximation and a full-potential linear-muffin-tin-orbital method. In both cases the arsenic sublattice was chosen to be continuous across the interface in accordance with experiments on Rutherford backscattering channeling. Band structures, densities of states, and charge density distributions were also determined for the interfaces. The comparison of the total supercell energies reveals that the gallium terminated (chain) interface is more energetically stable than the arsenic terminated (shadow) interface. It also shows that the equilibrium interface separation for the arsenic terminated interface corresponds to an ideal structure when arsenic forms undistorted face-centered cubic lattice. The separation in the gallium terminated interface is quite substantial and is 60% larger than that of the ideal situation. The model also predicts that no buckling of the ErAs interface monolayer will occur for either structure. The computed Schottky barriers for holes (after a semi-empirical quasiparticle self-energy correction) are 0.6 eV for the chain interface and 0.4 eV for the shadow interface.

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

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.

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

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.

Electronic and Optical Properties of Si/SiO2 Superlattices from First Principles: Role of Interfaces.

2001 ◽  
Vol 677 ◽  
Author(s):  
Pierre Carrier ◽  
Gilles Abramovici ◽  
Laurent J. Lewis ◽  
M. W. C. Dharma-wardana
Keyword(s):  
Optical Properties ◽  
First Principles ◽  
Energy Gap ◽  
Local Density ◽  
Interband Transition ◽  
Theoretical Research ◽  
Slab Thickness ◽  
Full Potential ◽  
Wave Method

ABSTRACTThe observation of intense luminescence in Si/SiO2 superlattices (SLs) has lead to new theoretical research on silicon-based materials. We have performed first-principles calculations using three Si/SiO2 SL models in order to examine the role of interfaces on the electronic structure and optical properties. The first two models are derived directly from crystalline structures and have simple interfaces. These models have been studied using the full-potential, linearized-augmented-plane-wave method, in the local-density-approximation (LDA). The optical absorption within the interband transition theory (excluding excitonic effects) have been deduced. The Si(001)-SiO2 interface structure is shown to affect the optical behaviour. Following these observations, we have considered a more realistic, fully-relaxed model. The projector-augmented-wave method under the LDA is used to perform the structural relaxation as well as band structure and optical calculations. The role of confinement on the energy gap is studied by inserting additional silicon slabs into the supercell. Direct energy gaps are observed and the energy gap is found to decrease with increasing silicon slab thickness, as observed experimentally. The role of the interface has been considered in more details by studying the contribution to the energy gap of Si atoms having different oxidation patterns; partially oxidized Si atoms at the interface, as well as Si atoms inside the Si layer, are shown to contribute to the transitions at the energy gap.

First-principles calculations to investigate structural, electronic and optical properties of (ZnSe)n/(ZnTe)n superlattices

2020 ◽  
Author(s):  
Messaoud Caid
Keyword(s):  
Optical Properties ◽  
First Principles ◽  
Density Functional ◽  
Correlation Energy ◽  
Local Density ◽  
Full Potential ◽  
First Principles Calculations ◽  
Electronic And Optical Properties ◽  
Lmto Method ◽  
Binary Compounds

An investigation into the structural, electronic and optical properties of superlattices(SLs) (ZnSe)n/(ZnTe)n was conducted using first principles calculations based on density functional theory (DFT). The total energies were calculated within the full-potential linear muffin-tin orbital (FP-LMTO) method augmented by a plane-wave basis (PLW), implemented in LmtART 7.0 code. The effects of the approximations to the exchange-correlation energy were treated by the local density approximation (LDA). The ground state properties of (ZnSe)n/(ZnTe)n binary compounds are determined and compared with the available data. It is found that the superlattice (n-n: 1-1, 2-2 and 3-3) band gaps vary depending on the layers used. The optical constants, including the dielectric function ε(w), the refractive index n(w) and the reflectivity R(w), are calculated for radiation energies up to 35eV.

A simple model for calculating the compressibility of the transition-metal carbides and nitrides alloys ZrxNb1−xC and ZrxNb1−xN

Open Physics ◽  
2011 ◽  
Vol 9 (5) ◽  
Author(s):  
Vassiliki Katsika-Tsigourakou
Keyword(s):  
First Principles ◽  
Local Density ◽  
Plane Waves ◽  
Ternary Alloys ◽  
Full Potential ◽  
First Principles Calculations ◽  
Metal Carbides ◽  
Rocksalt Structure ◽  
Mechanical And Physical Properties ◽  
End Members

AbstractThe 4d-transition-metals carbides (ZrC, NbC) and nitrides (ZrN, NbN) in the rocksalt structure, as well as their ternary alloys, have been recently studied by means of a first-principles full potential linearized augmented plane waves method within the local density approximation. These materials are important because of their interesting mechanical and physical properties, which make them suitable for many technological applications. Here, by using a simple theoretical model, we estimate the bulk moduli of their ternary alloys ZrxNb1−xC and ZrxNb1−xN in terms of the bulk moduli of the end members alone. The results are comparable to those deduced from the first-principles calculations.

scholarly journals A First-Principles Study of the Phase Stability of FCC-Based Ti-Al Alloys

1992 ◽  
Vol 278 ◽  
Author(s):  
Mark Asta ◽  
Didier De Fontaine ◽  
Mark Van Schilfgaarde ◽  
Marcel Sluiter ◽  
Michael Methfessel
Keyword(s):  
Phase Stability ◽  
First Principles ◽  
Cluster Variation Method ◽  
Stability Study ◽  
Al Alloys ◽  
Variation Method ◽  
Orbital Method ◽  
Temperature Phase ◽  
Full Potential ◽  
Cluster Variation

AbstractIn this paper we present results of a first-principles phase stability study of fcc-based Ti-Al alloys. In particular, the full-potential linear muffin tin orbital method has been used to determine heats of formation and other zero-temperature properties of 9 fcc ordered superstructures as well as fcc and hcp Ti, and fcc Al. From these results a set of effective cluster interactions are determined which are used in a cluster variation method calculation of the thermodynamic properties and the composition-temperature phase diagram of fcc-based alloys.

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