scholarly journals First-Principles Study of the Stabilization and Mechanical Properties of Rare-Earth Ferritic Perovskites (RFeO3, R = La, Eu, Gd)

2020 ◽  
Vol 10 (11) ◽  
pp. 4008
Author(s):  
Mahdi Faghihnasiri ◽  
Vahid Najafi ◽  
Farzaneh Shayeganfar ◽  
Ali Ramazani
Keyword(s):  
Mechanical Properties ◽  
Rare Earth ◽  
First Principles ◽  
Density Functional ◽  
Mechanical Response ◽  
External Loading ◽  
Chemical Bonds ◽  
Functional Theory ◽  
Density Values ◽  
The Stability

Current research aims to investigate the mechanical properties of rare earth perovskite ferrites (RFeO3, R = La, Eu, Gd) utilizing density functional theory (DFT) calculations. Using the revised Perdew–Burke–Ernzerhof approximation for solids (PBEsol) approximation, the elastic constants, bulk, Young’s, and shear modulus, Poisson’s ratio, and anisotropic properties are calculated. The quantum theory of atoms in molecules (QTAIM) is employed to analyze the stability of chemical bonds in the structures subjected to an external loading. Based on these calculations, Fe-O and R-O bonds can be considered as nearly ionic, which is due to the large difference in electronegativity of R and Fe with O. Additionally, our results reveal that the charge density values of the Fe-O bonds in both structures remain largely outside of the ionic range. Finally, the mechanical response of LaFeO3, EuFeO3, and GdFeO3 compounds to various cubic strains is investigated. The results show that in RFeO3 by increasing the radius of the lanthanide atom, the mechanical properties of the material including Young’s and bulk modulus increase.

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.

Site preference and atomic ordering in the ternary Rh5Ga2As: first-principles calculations

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Nilanjan Roy ◽  
Sucharita Giri ◽  
Harshit ◽  
Partha P. Jana
Keyword(s):  
Total Energy ◽  
First Principles ◽  
Density Functional ◽  
Structure Type ◽  
Site Preference ◽  
X Ray Diffraction ◽  
Atomic Ordering ◽  
Functional Theory ◽  
The Stability ◽  
Bonding Characteristics

Abstract The site preference and atomic ordering of the ternary Rh5Ga2As have been investigated using first-principles density functional theory (DFT). An interesting atomic ordering of two neighboring elements Ga and As reported in the structure of Rh5Ga2As by X-ray diffraction data only is confirmed by first-principles total-energy calculations. The previously reported experimental model with Ga/As ordering is indeed the most stable in the structure of Rh5Ga2As. The calculation detected that there is an obvious trend concerning the influence of the heteroatomic Rh–Ga/As contacts on the calculated total energy. Interestingly, the orderly distribution of As and Ga that is found in the binary GaAs (Zinc-blende structure type), retained to ternary Rh5Ga2As. The density of states (DOS) and Crystal Orbital Hamiltonian Population (COHP) are calculated to enlighten the stability and bonding characteristics in the structure of Rh5Ga2As. The bonding analysis also confirms that Rh–Ga/As short contacts are the major driving force towards the overall stability of the compound.

scholarly journals The stability and electronic and photocatalytic properties of the ZnWO4 (010) surface determined from first-principles and thermodynamic calculations

RSC Advances ◽  
2021 ◽  
Vol 11 (38) ◽  
pp. 23477-23490
Author(s):  
Yonggang Wu ◽  
Jihua Zhang ◽  
Bingwei Long ◽  
Hong Zhang
Keyword(s):  
Phase Diagram ◽  
Density Functional Theory ◽  
First Principles ◽  
Density Functional ◽  
Thermodynamic Calculations ◽  
Photocatalytic Properties ◽  
Thermodynamic Approach ◽  
Functional Theory ◽  
Stability Phase Diagram ◽  
The Stability

The ZnWO4 (010) surface termination stability is studied using a density functional theory-based thermodynamic approach. The stability phase diagram shows that O-Zn, DL-W, and DL-Zn terminations of ZnWO4 (010) can be stabilized.

The tuning effect of the electric field on the physical properties of some typical wurtzite semiconductors

2017 ◽  
Vol 31 (33) ◽  
pp. 1750310 ◽  
Author(s):  
Jia-Ning Li ◽  
San-Lue Hu ◽  
Hao-Yu Dong ◽  
Xiao-Ying Xu ◽  
Jia-Fu Wang ◽  
...  
Keyword(s):  
Electric Field ◽  
Physical Properties ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Great Influence ◽  
Semiconductor Materials ◽  
Functional Theory ◽  
The Stability ◽  
Wurtzite Semiconductors

Under the tuning of an external electric field, the variation of the geometric structures and the band gaps of the wurtzite semiconductors ZnS, ZnO, BeO, AlN, SiC and GaN have been investigated by the first-principles method based on density functional theory. The stability, density of states, band structures and the charge distribution have been analyzed under the electric field along (001) and (00[Formula: see text]) directions. Furthermore, the corresponding results have been compared without the electric field. According to our calculation, we find that the magnitude and the direction of the electric field have a great influence on the electronic structures of the wurtzite materials we mentioned above, which induce a phase transition from semiconductor to metal under a certain electric field. Therefore, we can regulate their physical properties of this type of semiconductor materials by tuning the magnitude and the direction of the electric field.

First-principles study of phase stability, electronic and mechanical properties of plutonium sub-oxides

2019 ◽  
Vol 21 (30) ◽  
pp. 16818-16829 ◽  
Author(s):  
P. S. Ghosh ◽  
A. Arya
Keyword(s):  
Mechanical Properties ◽  
Density Functional Theory ◽  
Phase Stability ◽  
First Principles ◽  
Density Functional ◽  
Functional Theory ◽  
First Principles Study ◽  
Hubbard Parameter ◽  
Formation Energies

Formation energies of PuO2, α-Pu2O3 and sub-oxides PuO2−x (0.0 < x < 0.5) are determined using density functional theory employing generalised gradient approximation corrected with an effective Hubbard parameter.

The effect of Ru on Ti50Pd50 high temperature shape memory alloy: a first-principles study

MRS Advances ◽  
2019 ◽  
Vol 4 (44-45) ◽  
pp. 2419-2429 ◽  
Author(s):  
R. G. Diale ◽  
R. Modiba ◽  
P. E. Ngoepe ◽  
H. R. Chauke
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Lattice Parameter ◽  
Heat Of Formation ◽  
Partial Substitution ◽  
Martensitic Transformation Temperature ◽  
Functional Theory ◽  
Equilibrium Lattice Parameter ◽  
Strengthening Element ◽  
The Stability

ABSTRACTThe stability of the Ti50Pd50-xRux alloy was investigated using first-principles density functional theory within the plane-wave pseudopotential method. Firstly, the Ti50Pd50 gave equilibrium lattice parameter and lowest heats of formation in better agreement with experimental data to within 3%. The heat of formation decreases with an increase in Ru concentration, consistent with the trend of the density of states which is lowered at the Fermi level as Ru content is increased which suggests stability. It was also found that from the calculated elastic constants the structures showed positive shear modulus above 20 at. % Ru, condition of stability. Furthermore, the addition of Ru was found to strengthen the Ti50Pd50-xRux system at higher concentrations. The thermal coefficients of linear expansion for the Ti50Pd31.25Ru18. 75 are higher at low temperature, and that the TiPd-Ru system tends to expand more at low content of 18.75 at. % Ru than at higher content. Partial substitution of Pd with Ru was found more effective as a strengthening element and may enhance the martensitic transformation temperature of the Ti50Pd50 alloy.

Calculation of electronic structure and mechanical properties of DO3–Fe75-xSi25Nix intermetallic compounds by first principles

2015 ◽  
Vol 29 (13) ◽  
pp. 1550087
Author(s):  
R. Ma ◽  
M. P. Wan ◽  
J. Huang ◽  
Q. Xie
Keyword(s):  
Mechanical Properties ◽  
Intermetallic Compounds ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Elastic Parameters ◽  
Functional Theory ◽  
Ni Content ◽  
The Density Functional Theory ◽  
The Difference

Based on the density functional theory (DFT), the plane-wave pseudopotential method was used to investigate the electronic structures and mechanical properties of DO 3– Fe 75-x Si 25 Ni x(x = 0, 3.125, 6.25 and 9.375) intermetallic compounds. The elastic parameters were calculated, and then the bulk modulus, shear modulus and elastic modulus were derived. The paper then focuses on the discussion of ductility and plasticity. The results show that by adding appropriate Ni to Fe 3 Si intermetallic compound can improve the ductility. But the hardness will increase when the Ni content exceeds 6.25%. Analysis of density of states (DOS) and overlap populations indicates that with the difference of the strength of bonding and activity, there were some differences of ductility among different Ni contents. The Fe 71.875 Ni 3.125 Si 25 has the lowest hardness because the covalent bonding (Fe–Si bond and Si–Ni bond) has the minimum covalent electrons.

First-Principles Study of the Electronic Structure and Spontaneous Polarization of PbZr0.4Ti0.6O3

2009 ◽  
Vol 79-82 ◽  
pp. 1249-1252 ◽  
Author(s):  
Qing Xun Zhao ◽  
Bo Geng ◽  
Li Guan ◽  
Qiang Li ◽  
Ji Kui Ma ◽  
...  
Keyword(s):  
Spontaneous Polarization ◽  
First Principles ◽  
Density Functional ◽  
Structural Data ◽  
Relative Displacement ◽  
Functional Theory ◽  
Bonding Interaction ◽  
Short Range Repulsion ◽  
Key Factor ◽  
The Stability

Density functional theory plane-wave pseudopotential with the general gradient approximation (GGA) was used to investigate electronic structural properties and the bulk spontaneous polarization (Ps) of PbZr0.4Ti0.6O3. It is found that there are strong hybridizations between Ti 3d states or Zr 4d states and O 2p states, which can reduce short-range repulsion in atoms and enhance the stability of the ferroelectric phase of PbZr0.4Ti0.6O3. Compared with cubic ideal structure, the calculated internal electronic structural data indicate that the slightly distorted O6 octahedrons around the central Ti and Zr atoms change to the Ti-O5 and Zr-O5 pyramid in the optimized structure, respectively. The major contribution to the spontaneous polarization along [001] comes from the stronger interaction along the c axis between the Ti and O rather than the Zr and O ions. The Pb atom’s relative displacement of oxygen octahedral implies that the Pb-O bonding interaction is also a key factor impacting the ferroelectricity of PbZr0.4Ti0.6O3. A theoretical spontaneous polarization of 0.78 C/m2 was computed in the tetragonal PbZr0.4Ti0.6O3 along [001] direction, consistent with the single crystal experimental data.

SPIN-POLARIZATION-DEPENDENT TRANSPORT IN GRAPHENE NANORIBBON WITH A VACANCY

2011 ◽  
Vol 10 (03) ◽  
pp. 533-538 ◽  
Author(s):  
CHUN-MEI LIU ◽  
NIAN-HUA LIU ◽  
ZHENG-FANG LIU ◽  
LI-PING AN
Keyword(s):  
Spin Polarization ◽  
Electronic Transport ◽  
First Principles ◽  
Density Functional ◽  
Graphene Nanoribbons ◽  
Electronic Band ◽  
Functional Theory ◽  
Electronic Band Gap ◽  
The Stability ◽  
Dependent Transport

By using the first-principles density functional theory combining with the nonequilibrium Green’s function techniques, we investigate the electronic structure and the spin-polarization-dependent electronic transport of zigzag graphene nanoribbons (ZGNR) with a defect of vacancy. The total energy of the graphene ribbons corresponding to different vacancy locations is calculated to analyze the stability of the structures. It is found that the existence of a vacancy causes a significant change in the electronic band gap. The electronic band and the transport become spin-polarization-dependent. The calculated I–V characteristic shows that the spin-polarization-dependent effect can be enhanced under a finite bias voltage.

Ab Initio Study of the Structural and Mechanical Properties of Hf-Si-N

2010 ◽  
Vol 139-141 ◽  
pp. 22-25 ◽  
Author(s):  
Xin Tan ◽  
Yu Qing Li ◽  
Xue Jie Liu ◽  
De Gong Liu
Keyword(s):  
Mechanical Properties ◽  
First Principles ◽  
Cohesive Energy ◽  
Density Functional ◽  
Substitutional Solid Solution ◽  
Lattice Parameter ◽  
Solution Phase ◽  
First Principles Calculations ◽  
Functional Theory ◽  
The Density Functional Theory

The structural and elastic properties of HfN and Hf-Si-N have been studied, using first principles calculations based on the density functional theory. These calculations provide the lattice parameter, cohesive energy and elastic constants of fcc (NaCl)-HfN, the N-deficient Hf-Si-N and the Hf-deficient Hf-Si-N solution phase. In order to study the relative stability, binding energy of all configurations has been calculated. The results showed that it was difficult to add a Si atom into the center of the HfN cell because the cohesive energy decreased. However, if an Hf atom or an N atom was missing in the HfN, a silicon atom was possible to occupy the vacant site and form the Hf-Si-N substitutional solid solution. Moreover, the bulk modulus, shear modulus and elastic modulus increased accordingly, the mechanical properties were improved.

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