First-principles investigation of bandgap tailoring in tetragonal Bi2FeCrO6 by magnetic ordering and B-site-cation ordering

2019 ◽  
Vol 13 (01) ◽  
pp. 1950092
Author(s):  
Lijing Wei ◽  
Jianxin Guo ◽  
Li Guan ◽  
Baoting Liu
Keyword(s):  
First Principles ◽  
Magnetic Ordering ◽  
Stable Structure ◽  
Cation Ordering ◽  
First Principles Calculations ◽  
Antiferromagnetic Ordering ◽  
Long Time ◽  
Application Potential

The development of ferroelectric photovoltaic (FE-PV) materials has been limited for a long time due to their large bandgap. Many strategies for lowering the bandgap have been suggested to promote FE-PV properties. The effects of magnetic ordering and B-site-cation ordering to lower the bandgap of FE-PV are investigated in this paper using first-principles calculations. Results show that the most stable structure of tetragonal Bi2FeCrO6 ([Formula: see text]-Bi2[Formula: see text] is the AS1 structure (Fe/Cr alternate stacking ordering) with C-type antiferromagnetic ordering (defined as AC-[Formula: see text]-Bi2FeCrO6), which has a small bandgap, suggesting that AC-[Formula: see text]-Bi2FeCrO6 is among the FE-PV materials with the highest application potential.

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

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 100 ◽  
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.

Structural analysis of Gd6FeBi2 from single-crystal X-ray diffraction methods and electronic structure calculations

2019 ◽  
Vol 75 (5) ◽  
pp. 562-567 ◽  
Author(s):  
Jiliang Zhang ◽  
Yong-Mook Kang ◽  
Guangcun Shan ◽  
Svilen Bobev
Keyword(s):  
Electronic Structure ◽  
Single Crystal ◽  
First Principles ◽  
Earth Metal ◽  
Magnetic Ordering ◽  
Additional Contribution ◽  
First Principles Calculations ◽  
X Ray Diffraction ◽  
Magnetic Exchange ◽  
X Ray

The crystal structure of the gadolinium iron bismuthide Gd6FeBi2 has been characterized by single-crystal X-ray diffraction data and analyzed in detail using first-principles calculations. The structure is isotypic with the Zr6CoAl2 structure, which is a variant of the ZrNiAl structure and its binary prototype Fe2P (Pearson code hP9, Wyckoff sequence g f d a). As such, the structure is best viewed as an array of tricapped trigonal prisms of Gd atoms centered alternately by Fe and Bi. The magnetic-ordering temperature of this compound (ca 350 K) is much higher than that of other rare-earth metal-rich phases with the same or related structures. It is also higher than the ordering temperature of many other Gd-rich ternary phases, where the magnetic exchange is typically governed by Ruderman–Kittel–Kasuya–Yosida (RKKY) interactions. First-principles calculations reveal a larger than expected Gd magnetic moment, with the additional contribution arising from the Gd 5d electrons. The electronic structure analysis suggests strong Gd 5d–Fe 3d hybridization to be the cause of this effect, rather than weak interactions between Gd and Bi. These details are of importance for understanding the magnetic response and explaining the high ordering temperature in this material.

scholarly journals Structure and cation ordering in La2UO6, Ce2UO6, LaUO4, and CeUO4 by first principles calculations

2016 ◽  
Vol 123 ◽  
pp. 201-213 ◽  
Author(s):  
L. Casillas-Trujillo ◽  
H. Xu ◽  
J.W. McMurray ◽  
D. Shin ◽  
G. Baldinozzi ◽  
...  
Keyword(s):  
First Principles ◽  
Cation Ordering ◽  
First Principles Calculations

Electronic structure and magnetic ordering in gadolinium-doped AlGaN from LSDA + U calculations

2018 ◽  
Vol 07 (03) ◽  
pp. 1850019 ◽  
Author(s):  
S. Belhachi ◽  
S. Amari ◽  
B. Bouhafs
Keyword(s):  
Density Functional Theory ◽  
Magnetic Properties ◽  
Band Gap ◽  
First Principles ◽  
Density Functional ◽  
Magnetic Ordering ◽  
First Principles Calculations ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Indirect Band Gap

We present first-principles calculations of the structural, electronic and magnetic properties of Gd-doped [Formula: see text] based on the density functional theory within [Formula: see text] schemes. It is found that Gd atom favors substituting for Al site. Compared with undoped [Formula: see text], the Gd-doped [Formula: see text] has become an indirect band gap semiconductor of reduced band gap. The magnetic moment [Formula: see text] per molecule mainly comes from Gd ion with little contribution from the Ga, Al and N atoms. It is confirmed that the ferromagnetic configuration is stable for [Formula: see text]. It is found also that there is hybridization between the forbital of the Gd atom and the [Formula: see text] orbital of the N atom.

Highly Tunable Electronic Structure and Linear Dichroism in 90° Twisted α-Phosphorus Carbide Bilayer: A First-Principles Calculation

2021 ◽  
Author(s):  
Weiwei Liu ◽  
Hongwei Bao ◽  
Yan Li ◽  
Fei Ma
Keyword(s):  
Electronic Structure ◽  
First Principles ◽  
Carrier Mobility ◽  
Electronic Devices ◽  
Linear Dichroism ◽  
First Principles Calculation ◽  
First Principles Calculations ◽  
Application Potential ◽  
High Carrier Mobility ◽  
High Carrier

α-phosphorus carbide (α-PC) shares similar puckered structure with black phosphorus and has a high carrier mobility, showing great application potential in the future nano-electronic devices. Based on first-principles calculations, we...

scholarly journals Influence of inversion on Mg mobility and electrochemistry in spinels

2017 ◽  
Author(s):  
Gopalakrishnan Sai Gautam ◽  
Pieremanuele Canepa ◽  
Alexander Urban ◽  
Shou-Hang Bo ◽  
Gerbrand Ceder
Keyword(s):  
First Principles ◽  
Ionic Mobility ◽  
Limiting Factor ◽  
Cation Ordering ◽  
First Principles Calculations ◽  
Synthesis Conditions ◽  
Migration Barriers ◽  
Percolation Thresholds ◽  
Migration Pathways ◽  
The Impact

<div> <div> <div> <p>Magnesium oxide and sulfide spinels have recently attracted interest as cathode and electrolyte materials for energy-dense Mg batteries, but their observed electrochemical performance depends strongly on synthesis conditions. Using first principles calculations and percolation theory, we explore the extent to which spinel inversion influences Mg2+ ionic mobility in MgMn2O4 as a pro- totypical cathode, and MgIn2S4 as a potential solid electrolyte. We find that spinel inversion and the resulting changes of the local cation ordering give rise to both increased and decreased Mg2+ migration barriers, along specific migration pathways, in the oxide as well as the sulfide. </p> <p>To quantify the impact of spinel inversion on macroscopic Mg2+ transport, we determine the percolation thresholds in both MgMn2O4 and MgIn2S4. Furthermore, we analyze the impact of inversion on the electrochemical properties of the MgMn2O4 cathode via changes in the phase behavior, average Mg insertion voltages and extractable capacities, at varying degrees of inversion. Our results confirm that inversion is a major performance limiting factor of Mg spinels and that synthesis techniques or compositions that stabilize the well-ordered spinel structure are crucial for the success of Mg spinels in multivalent batteries. </p> </div> </div> </div>

Charge, Orbital, and Magnetic Ordering in YBaFe2O5from First-Principles Calculations

2008 ◽  
Vol 47 (11) ◽  
pp. 4734-4739 ◽  
Author(s):  
Xianfeng Hao ◽  
Yuanhui Xu ◽  
Minfeng Lv ◽  
Defeng Zhou ◽  
Zhijian Wu ◽  
...  
Keyword(s):  
First Principles ◽  
Magnetic Ordering ◽  
First Principles Calculations

scholarly journals First-Principles Calculations of the Electronic Structure and Optical Properties of Yttrium-Doped ZnO Monolayer with Vacancy

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 724
Author(s):  
Qian Wu ◽  
Ping Wang ◽  
Yan Liu ◽  
Han Yang ◽  
Jingsi Cheng ◽  
...  
Keyword(s):  
Oxygen Vacancy ◽  
First Principles ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Light Region ◽  
Application Potential ◽  
Doped Zno

The electronic structures and optical characteristics of yttrium (Y)-doped ZnO monolayers (MLs) with vacancy (zinc vacancy, oxygen vacancy) were investigated by the first-principles density functional theory. Calculations were performed with the GGA+U (generalized gradient approximation plus U) approach, which can accurately estimate the energy of strong correlation semiconductors. The results show that the formation energy values of Y-doped ZnO MLs with zinc or oxygen vacancy (VZn, VO) are positive, implying that the systems are unstable. The bandgap of Y-VZn-ZnO was 3.23 eV, whereas that of Y-VO-ZnO was 2.24 eV, which are smaller than the bandgaps of pure ZnO ML and Y-doped ZnO MLs with or without VO. Impurity levels appeared in the forbidden band of ZnO MLs with Y and vacancy. Furthermore, Y-VZn-ZnO will result in a red-shift of the absorption edge. Compared with the pure ZnO ML, ZnO MLs with one defect (Y, VZn or VO), and Y-VZn-ZnO, the absorption coefficient of Y-VO-ZnO was significantly enhanced in the visible light region. These findings demonstrate that Y-VO-ZnO would have great application potential in photocatalysis.

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