Surface energies and relaxation of NiCoCr and NiFeX (X=Cu, Co or Cr) equiatomic multiprincipal element alloys from first principles calculations

2021 ◽  
Author(s):  
Wei Li ◽  
Xianghe Peng ◽  
Alfonso H W Ngan ◽  
Jaafar El-Awady
Keyword(s):  
First Principles ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
Principal Element ◽  
Fracture Properties ◽  
Catalytic Activities ◽  
Surface Energies ◽  
Generalized Gradient Approximation ◽  
Projector Augmented Wave ◽  
Cutting Model

Abstract First principles calculations of the energies and relaxation of unreconstructed low-index surfaces, i.e. (001), (011) and (111) surfaces, in NiCoCr and NiFeX (X=Cu, Co or Cr) equiatomic multi-principal element alloys are presented. The calculations were conducted for twelve-layer slabs represented by special quasi-random supercells using the projector augmented wave method within the generalized gradient approximation. While experimental predictions are unavailable for comparison, the calculated surface energies agree fairly well with those from thermodynamic modeling and a bond-cutting model. In addition, the calculations unveil an important surface structure, namely, that the topmost surface layer is in contraction except for the (001) surface of NiFeCr alloy, the next layer below is in extension, and the bulk spacing is gradually recovered from the subsequent layers down. Additionally, the surface contraction is the most pronounced on the (011) plane, being about 4-10% relative to the bulk spacings. The results presented here can provide an understanding of surface-controlled phenomena such as corrosion, catalytic activities and fracture properties in these equiatomic multi-principal element alloys.

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.

Barrier to Migration of the Intrinsic Defects in Silicon in Different Charged System Using First-principles Calculations

2005 ◽  
Vol 864 ◽  
Author(s):  
Jinyu Zhang
Keyword(s):  
Density Functional Theory ◽  
First Principles ◽  
Density Functional ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Diffusion Behavior ◽  
Generalized Gradient Approximation ◽  
Charged System ◽  
And Diffusion

AbstractUsing density functional theory (DFT) calculations within the generalized gradient approximation (GGA), we have investigated the structure, energies and diffusion behavior of Si defects including interstitial, vacancy, FFCD and divacancy in various charged states.

First Principles Calculations on Cu-Doped TiO2

2015 ◽  
Vol 1101 ◽  
pp. 70-74 ◽  
Author(s):  
Waqas Mahmood
Keyword(s):  
Optical Properties ◽  
Plane Wave ◽  
First Principles ◽  
Geometry Optimization ◽  
Titanium Atom ◽  
Mesh Size ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
Generalized Gradient Approximation ◽  
Cutoff Energy

The electronic and optical properties of tetragonal rutile TiO2 are investigated by first principles calculations using plane-wave pseudopotentials. Generalized gradient approximation proposed by Perdew-Burke-Ernzerhof (GGA-PBE) is employed with Vanderbilt’s ultrasoft pseudopotentials (USPs) for the geometry optimization. The cutoff energy 380 eV and Monkhorst-Pack (MP) grid of size 5 x 5 x 8 is used to study the electronic properties of TiO2. Besides, the optical properties of TiO2 are studied using a mesh size of 9 x 9 x 9. A periodic supercell of size 2a x 2b x 2c is created and a single Copper (Cu) atom directly substitutes the titanium atom. The geometry is optimized at cutoff energy 440 eV with MP grid of size 3 x 3 x 8 and a denser k-points mesh of size 6 x 6 x 6 is used for the investigation of optical properties.

Stability of α Phase in Ti Alloys Containing Al or Zr from First-Principles Calculations

2013 ◽  
Vol 634-638 ◽  
pp. 1831-1835
Author(s):  
Zhong Bo Zhou ◽  
Hong Chao Kou ◽  
Xiang Yi Xue ◽  
Hui Chang ◽  
Li Jun Zhang ◽  
...  
Keyword(s):  
First Principles ◽  
Plane Waves ◽  
Repulsive Interaction ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
Al Content ◽  
Generalized Gradient Approximation ◽  
Ti Alloys ◽  
Α Phase ◽  
The Stability

The energetic and electronic structure of α-type Ti1-xXx (X=Al and Zr, x=0.0625, 0.125, 0.185, 0.250, 0.3125and 0.375) binary alloys were calculated by the method of supercell and augmented plane waves plus local orbitals within generalized gradient approximation. The results show that the formation energy decreases with the composition of Al, while increases with composition of Zr, which indicate that α phase can be enhanced by increasing the Al contents while weaken by increasing Zr contents. The DOS results shows that the Fermi levels of Ti1-x Al x and Ti 1-x Zr x fall on a dip of a DOS curve, which means the α structure of these alloys is stable. When the Al content is increased, the charge transfer between the Al and its neighbors becomes more evident, and enhance the stability of the α phase. With an increase of Zr content, repulsive interaction between two Ti atoms strengthen, which result in the α phase stability decrease.

Optical Properties of β-Si3N4 Studied from First-Principles Method

2012 ◽  
Vol 490-495 ◽  
pp. 3253-3256 ◽  
Author(s):  
Dong Chen ◽  
Kui Yang
Keyword(s):  
Optical Properties ◽  
First Principles ◽  
Theoretical Study ◽  
Potential Method ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
Generalized Gradient Approximation ◽  
Near Future ◽  
Pseudo Potential ◽  
Good Agreement

A detailed theoretical study of the optical properties of β-Si3N4 has been carried out by means of first-principles calculations using the plane-wave pseudo-potential method with generalized gradient approximation for the exchange and correlation functional. The calculated maximum absorption coefficient is 312000, which is in good agreement with the other calculated result. β-Si3N4 can be used as a photo-electronic material because its absorption curve has an abrupt limit at low energy region. The light beam with the frequency of 7eV～15eV can easily traverse the β-Si3N4 crystal. For the dielectric function, the strongest peaks are located at 6.5 and 9.0eV for the real and imaginary parts, respectively. Moreover, the calculated static dielectric constant is 3.21. Actually speaking, our calculated results should be testified by experiments in the near future.

THERMAL PROPERTIES OF THE XB2(X = Ag, Au) COMPOUNDS: A FIRST-PRINCIPLES STUDY

2013 ◽  
Vol 27 (12) ◽  
pp. 1350046
Author(s):  
HAVVA BOGAZ OZISIK ◽  
KEMAL COLAKOGLU ◽  
ENGIN DELIGOZ
Keyword(s):  
Density Functional Theory ◽  
First Principles ◽  
Density Functional ◽  
Debye Model ◽  
First Principles Calculations ◽  
Correlation Effects ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Generalized Gradient Approximation

The thermodynamic properties of AgB 2 and AuB 2 compounds in AlB 2 and OsB 2-type structures are investigated from first-principles calculations based on density functional theory (DFT) using projector augmented waves (PAW) potentials within the generalized gradient approximation (GGA) for modeling exchange-correlation effects, respectively. Specifically, using the quasi-harmonic Debye model, the effects of pressure and temperature, up to 100 GPa and 1400 K, on the bulk modulus, Debye temperature, thermal expansion, heat capacity and the Grüneisen parameter are calculated successfully and trends are discussed.

Thermoelectric properties of half-Heusler ZrNiPb by using first principles calculations

RSC Advances ◽  
2016 ◽  
Vol 6 (53) ◽  
pp. 47953-47958 ◽  
Author(s):  
San-Dong Guo
Keyword(s):  
Thermoelectric Properties ◽  
First Principles ◽  
Electronic Structures ◽  
Orbit Coupling ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
Generalized Gradient Approximation

We investigate the electronic structures and thermoelectric properties of a recently synthesized half-Heusler ZrNiPb compound by using a generalized gradient approximation (GGA) and GGA plus spin–orbit coupling (GGA + SOC).

First-Principles Study of Structural and Thermal of α-Ni4N

2015 ◽  
Vol 817 ◽  
pp. 719-724 ◽  
Author(s):  
Hai Jun Hou ◽  
Hua Jun Zhu ◽  
Xiao Liang ◽  
Lin Hua Xie
Keyword(s):  
Thermal Expansion ◽  
Thermal Properties ◽  
Bulk Modulus ◽  
Elastic Constants ◽  
First Principles ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
Generalized Gradient Approximation ◽  
Debye Method ◽  
Good Agreement

This paper reports a study on the structure and elastic properties of cubic α-Ni4N by performing first principles calculations within Generalized gradient approximation (GGA). The calculated lattice constant and elastic constants are in good agreement with the available experimental or theoretical value. The thermal properties including the bulk modulus, thermal expansion, Grüneisen parameter and Debye temperature have also been calculated within the quasi-harmonic Debye method.

scholarly journals Ultimate Mechanical Properties of Forsterite

Minerals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 787 ◽  
Author(s):  
Karine Gouriet ◽  
Philippe Carrez ◽  
Patrick Cordier
Keyword(s):  
Mechanical Properties ◽  
First Principles ◽  
Shear Plane ◽  
Shear Loading ◽  
High Symmetry ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
Generalized Gradient Approximation ◽  
Homogeneous Strain ◽  
The Ideal

The ultimate mechanical properties, as characterized here by the ideal strengths of Mg2SiO4 forsterite, have been calculated using first-principles calculations and generalized gradient approximation under tensile and shear loading. The ideal tensile strengths (ITS) and ideal shear strengths (ISS) are computed by applying homogeneous strain increments along high-symmetry directions ([100], [010], and [001]) and low index shear plane ((100), (010), and (001)) of the orthorhombic lattice. We show that the ultimate mechanical properties of forsterite are highly anisotropic, with ITS ranging from 12.1 GPa along [010] to 29.3 GPa along [100], and ISS ranging from 5.6 GPa for simple shear deformation along (100) to 11.5 GPa for shear along (010).

Engineering the Topological Phase of Half Heusler Compounds by Computer

2015 ◽  
Vol 713-715 ◽  
pp. 2695-2698
Author(s):  
L.Y. Wang ◽  
S. Gao
Keyword(s):  
First Principles ◽  
Present Finding ◽  
Spin Orbit Coupling ◽  
Topological Phase ◽  
Heusler Compounds ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
Approximation Approach ◽  
Generalized Gradient Approximation ◽  
Band Inversion

Band inversion mechanisms of half Heusler compouds XMBi (X=Sc, Y, Lu, La, M=Pd, Pt) is investigated under different conditions, based on first-principles calculations with generalized gradient approximation approach. The results shown that Spin-orbit coupling, however, is not the leading cause but an account can add further fuel to the band inversion. The present finding provides an effective scheme to search for topologically nontrivial materials.

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