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

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.

Download Full-text

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

10.26434/chemrxiv.8052218.v3 ◽

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.

Download Full-text

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

Zeitschrift für Kristallographie - Crystalline Materials ◽

10.1515/zkri-2021-2019 ◽

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.

Download Full-text

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

RSC Advances ◽

10.1039/d1ra03218f ◽

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.

Download Full-text

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

Modern Physics Letters B ◽

10.1142/s0217984917503109 ◽

2017 ◽

Vol 31 (33) ◽

pp. 1750310 ◽

Cited By ~ 1

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.

Download Full-text

Effect of Defects on Spontaneous Polarization in Pure and Doped LiNbO3: First-Principles Calculations

Materials ◽

10.3390/ma12010100 ◽

2018 ◽

Vol 12 (1) ◽

pp. 100 ◽

Cited By ~ 5

Author(s):

Weiwei Wang ◽

Dahuai Zheng ◽

Mengyuan Hu ◽

Shahzad Saeed ◽

Hongde Liu ◽

...

Keyword(s):

Spontaneous Polarization ◽

First Principles ◽

Density Functional ◽

Lattice Distortion ◽

Stable Structure ◽

First Principles Calculations ◽

Functional Theory ◽

The Density Functional Theory ◽

Specific Configuration ◽

The Relationship

Numerous studies have indicated that intrinsic defects in lithium niobate (LN) dominate its physical properties. In an Nb-rich environment, the structure that consists of a niobium anti-site with four lithium vacancies is considered the most stable structure. Based on the density functional theory (DFT), the specific configuration of the four lithium vacancies of LN were explored. The results indicated the most stable structure consisted of two lithium vacancies as the first neighbors and the other two as the second nearest neighbors of Nb anti-site in pure LN, and a similar stable structure was found in the doped LN. We found that the defects dipole moment has no direct contribution to the crystal polarization. Spontaneous polarization is more likely due to the lattice distortion of the crystal. This was verified in the defects structure of Mg2+, Sc3+, and Zr4+ doped LN. The conclusion provides a new understanding about the relationship between defect clusters and crystal polarization.

Download Full-text

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

MRS Advances ◽

10.1557/adv.2019.331 ◽

2019 ◽

Vol 4 (44-45) ◽

pp. 2419-2429 ◽

Cited By ~ 1

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.

Download Full-text

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

Applied Sciences ◽

10.3390/app10114008 ◽

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.

Download Full-text

Experimental and DFT Studies of Au Deposition Over WO3/g-C3N4 Z-Scheme Heterojunction

Nano-Micro Letters ◽

10.1007/s40820-019-0345-2 ◽

2019 ◽

Vol 12 (1) ◽

Cited By ~ 9

Author(s):

Muhammad Humayun ◽

Habib Ullah ◽

Junhao Cao ◽

Wenbo Pi ◽

Yang Yuan ◽

...

Keyword(s):

Visible Light ◽

Density Functional ◽

Resonance Effect ◽

State Density ◽

Functional Theory ◽

Co Catalysts ◽

Redox Couples ◽

Bonding Interaction ◽

Wet Chemical ◽

The Stability

AbstractA typical Z-scheme system is composed of two photocatalysts which generate two sets of charge carriers and split water into H2 and O2 at different locations. Scientists are struggling to enhance the efficiencies of these systems by maximizing their light absorption, engineering more stable redox couples, and discovering new O2 and H2 evolutions co-catalysts. In this work, Au decorated WO3/g-C3N4 Z-scheme nanocomposites are fabricated via wet-chemical and photo-deposition methods. The nanocomposites are utilized in photocatalysis for H2 production and 2,4-dichlorophenol (2,4-DCP) degradation. It is investigated that the optimized 4Au/6% WO3/CN nanocomposite is highly efficient for production of 69.9 and 307.3 µmol h−1 g−1 H2 gas, respectively, under visible-light (λ > 420 nm) and UV–visible illumination. Further, the fabricated 4Au/6% WO3/CN nanocomposite is significant (i.e., 100% degradation in 2 h) for 2,4-DCP degradation under visible light and highly stable in photocatalysis. A significant 4.17% quantum efficiency is recorded for H2 production at wavelength 420 nm. This enhanced performance is attributed to the improved charge separation and the surface plasmon resonance effect of Au nanoparticles. Solid-state density functional theory simulations are performed to countercheck and validate our experimental data. Positive surface formation energy, high charge transfer, and strong non-bonding interaction via electrostatic forces confirm the stability of 4Au/6% WO3/CN interface.

Download Full-text

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

International Journal of Nanoscience ◽

10.1142/s0219581x11008307 ◽

2011 ◽

Vol 10 (03) ◽

pp. 533-538 ◽

Cited By ~ 1

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.

Download Full-text

Study on CH4 Adsorption onto the Surfaces of Perovskite ABO3 ( A=La, Ba; B=Zr, Co, Ce) by Density Functional Theory

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.291-294.1208 ◽

2011 ◽

Vol 291-294 ◽

pp. 1208-1211 ◽

Cited By ~ 1

Author(s):

Zi Shu Gao ◽

Hua An ◽

Li Lv ◽

Li Chun Hou ◽

Hui Han ◽

...

Keyword(s):

Density Functional Theory ◽

First Principles ◽

Density Functional ◽

Energy State ◽

Absorption Mechanism ◽

Functional Theory ◽

Key Factor ◽

A Site ◽

Perovskite Type ◽

Structure Calculations

The adsorption of CH4onto the surfaces of perovskite-type catalysts ABO3( A=La, Ba; B=Zr, Co, Ce) was investigated by a density functional theory based on the first-principles in this paper. The absorption mechanism was derived by population and electronic states analysis on the basis of the electronic and surface structure calculations. For A=Ba and B=Zr, the frontier energy state was found to the key factor in controlling the adsorption behavior of CH4absorbed on (001) surfaces, which is mainly contributed by oxygen and B-site ions. The most favorite adsorption site for CH4was located at B-sites of perovskite catalysts ABO3, where the A-site ions adjust the charge of B-site ions and moreover affect the CH4adsorption.

Download Full-text