Effects of nonmetal doping on electronic structures of NaNbO3 based on hybrid density functional calculation

The influences of a series of anion doping on the electronic structures of sodium niobate (NaNbO3) have been systematically investigated by density functional theory (DFT) calculations with the hybrid B3LYP functional. As for B[Formula: see text](C,[Formula: see text]P)-doped NaNbO3, the isolated B 2p (C 2p, P 3p) states were formed above the valence band maximum (VBM) of NaNbO3, which were too weak to mix with O 2p states and thus produced band gap narrowing. While the band gap of NaNbO3 was slightly narrowed after F doping. As for S-doped NaNbO3, the S 3p states mixed with O 2p states well and thus reduced the band gap energy. According to the calculation results, we tentatively put forward that S doping would be appropriate for single anion doping NaNbO3, while the B[Formula: see text](C,[Formula: see text]P) elements would be suitable candidates for co-doping NaNbO3.

Download Full-text

FIRST-PRINCIPLES CALCULATIONS ON ELECTRONIC STRUCTURES OF TiO2 ANATASE (101) SURFACES WITH N IMPURITIES

Modern Physics Letters B ◽

10.1142/s0217984911025535 ◽

2011 ◽

Vol 25 (02) ◽

pp. 119-129 ◽

Cited By ~ 4

Author(s):

QI LI CHEN ◽

GUANG ZHENG ◽

KAI HUA HE ◽

BO LI

Keyword(s):

Band Gap ◽

Electronic Structures ◽

Density Functional ◽

First Principles Calculations ◽

Functional Theory ◽

Tio2 Anatase ◽

Exchange Correlation ◽

N Doping ◽

Band Gap Narrowing ◽

Coefficient Method

The electronic structures of nitrogen ( N )-doped TiO 2 anatase (101) surfaces have been investigated by density functional theory (DFT) plane-wave pseudopotential method with general gradient approximation (GGA) + U (Hubbard coefficient) method being adopted to describe the exchange-correlation effects. Both substitutional and interstitial N doping have been considered in this paper as well as the case of surface N adsorption. The results demonstrated that there is no obvious band gap narrowing observed by introducing N impurities except several N 2p states lying in the gap, whereas the introduction of oxygen vacancy was confirmed playing an important role on band gap narrowing. The results accord well with some experimental results.

Download Full-text

First-Principles Calculations on Pure and Y-Doped Anatase TiO2

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.562-565.1166 ◽

2013 ◽

Vol 562-565 ◽

pp. 1166-1170 ◽

Cited By ~ 1

Author(s):

Xiong Tang ◽

Lan Fang Yao ◽

Xin Pei Yan ◽

Jun Long Kang

Keyword(s):

Band Gap ◽

First Principles ◽

Density Functional ◽

Correlation Energy ◽

Partial Density ◽

First Principles Calculations ◽

Generalized Gradient ◽

Functional Theory ◽

Calculation Results ◽

Band Gap Narrowing

Using the First principles calculations, the crystal structure, band gap, total and partial density of states (DOS) of anatase TiO2and anatase TiO2doped with Yttrium were calculated by a plane-wave pseudopotential (PWPP) method based on density functional theory (DFT). The generalized gradient approximation (GGA) based on exchange-correlation energy optimization was employed to calculate them. From the calculation results, the band gap of anatase TiO2and Y3+doped TiO2are about 2.15eV and 0.86eV. The calculated results demonstrated that the mixing of Yttrium (Y) dopants induces states with original titanium 3d and oxygen 2p valence band attributes to the band gap narrowing. This can enhance the photocatalytic activity of anatase TiO2.

Download Full-text

Comparative Study on Electronic Structure and Optical Properties of α-Fe2O3, Ag/α-Fe2O3 and S/α-Fe2O3

Metals ◽

10.3390/met11030424 ◽

2021 ◽

Vol 11 (3) ◽

pp. 424

Author(s):

Cuihua Zhao ◽

Baishi Li ◽

Xi Zhou ◽

Jianhua Chen ◽

Hongqun Tang

Keyword(s):

Optical Properties ◽

Optical Absorption ◽

Electronic Structures ◽

Density Functional ◽

Peak Strength ◽

Visible Range ◽

High Symmetry ◽

Functional Theory ◽

Optical Absorption Peak ◽

Calculation Results

The electronic structures and optical properties of pure, Ag-doped and S-doped α-Fe2O3 were studied using density functional theory (DFT). The calculation results show that the structure of α-Fe2O3 crystal changes after Ag and S doping, which leads to the different points of the high symmetry of Ag-doped and S-doped α-Fe2O3 with that of pure α-Fe2O3 in the energy band, as well as different Brillouin paths. In addition, the band gap of α-Fe2O3 becomes smaller after Ag and S doping, and the optical absorption peak shifts slightly toward the short wavelength, with the increased peak strength of S/α-Fe2O3 and the decreased peak strength of Ag/α-Fe2O3. However, the optical absorption in the visible range is enhanced after Ag and S doping compared with that of pure α-Fe2O3 when the wavelength is greater than 380 nm, and the optical absorption of S-doped α-Fe2O3 is stronger than that of Ag-doped α-Fe2O3.

Download Full-text

On the molecular modeling analyses of sodium carboxymethyl cellulose treated with acetic acid

Letters in Applied NanoBioScience ◽

10.33263/lianbs82.553557 ◽

2019 ◽

Vol 8 (2) ◽

pp. 553-557 ◽

Cited By ~ 1

Keyword(s):

Acetic Acid ◽

Band Gap ◽

Carboxymethyl Cellulose ◽

Density Functional ◽

Band Gap Energy ◽

Sodium Carboxymethyl Cellulose ◽

Functional Theory ◽

Gap Energy ◽

Model Molecule ◽

Homo Lumo

Model molecules for sodium carboxymethyl cellulose (Na-CMC) (monomer), glycerol, acetic acid and Na-CMC-glycerol-acetic acid are optimized with Density Functional Theory (DFT) at B3LYP/3-21G*. For the optimized models, total dipole moment (TDM), the highest occupied and lowest unoccupied molecular orbitals (HOMO/LUMO band gap energy), and molecular electrostatic potentials (ESP) are calculated at the same method to give an explanation for the possibility of using Na-CMC-Glycerol-acetic acid model molecule in electrochemical devices, gas sensors and batteries. As a result of the substitution of Na-CMC with glycerol, TDM increased from 7.7141 Debye to 22.4942 Debye which is approximately equal to three times that of Na-CMC. However, HOMO/LUMO band gap energy decreased from 0.9040 eV to 0.5072 eV. After the addition of acetic acid to Na-CMC-glycerol model, TDM increased to24.7270 Debye and HOMO/LUMO band gap energy decreased to 0.4939 eV. Both TDM and HOMO/LUMO band gap energy values are improved by increasing the acetic acid units, where TDM became 25.3510 Debye and HOMO/LUMO band gap energy decreased to 0.3815 eV. The results of ESP indicated that the addition of glycerol and acetic acid to Na-CMC increased the electronegativity of Na-CMC which in turn enhanced its electronic properties.

Download Full-text

Understanding Persistent Luminescence: Rare-Earth- and Eu2+-doped Sr2MgSi2O7

Zeitschrift für Naturforschung B ◽

10.5560/znb.2014-3322 ◽

2014 ◽

Vol 69 (2) ◽

pp. 171-182 ◽

Cited By ~ 11

Author(s):

Mika Lastusaari ◽

Högne Jungner ◽

Aleksei Kotlov ◽

Taneli Laamanen ◽

Lucas C. V. Rodrigues ◽

...

Keyword(s):

Rare Earth ◽

Band Gap ◽

Charge Compensation ◽

Band Gap Energy ◽

Persistent Luminescence ◽

Excitation Spectra ◽

Co Doping ◽

The Individual ◽

Initial Intensity ◽

The Eu

Similar to many other Eu2+,RE3+-co-doped persistent luminescence materials, for Sr2MgSi2O7:Eu2+,RE3+ the initial intensity and duration of persistent luminescence was also found to depend critically on the rare-earth (RE) co-doping. An enhancement of 1 - 2 orders of magnitude in these properties could be obtained by Dy3+ co-doping whereas total quenching of persistent luminescence resulted from the use of Sm3+ and Yb3+. To solve this drastic disparity, the effects of the individual RE3+ ions were studied with thermoluminescence (TL) spectroscopy to derive information about the formation of traps storing the excitation energy. The charge compensation defects were concluded to be the origin of the complex TL glow curve structure. The tuning of the band gap of the Sr2MgSi2O7 host and especially the position of the bottom of the conduction band due to the Eu2+,RE3+ co-doping was measured with the synchrotron radiation vacuum UV (VUV) excitation spectra of the Eu2+ dopant. The model based on the evolution of the band gap energy with RE3+ co-doping was found to explain the intensity and duration of the persistent luminescence.

Download Full-text

Carbon-Based Band Gap Engineering in the h-BN Analytical Modeling

Materials ◽

10.3390/ma13051026 ◽

2020 ◽

Vol 13 (5) ◽

pp. 1026

Author(s):

Mohammad Taghi Ahmadi ◽

Ahmad Razmdideh ◽

Seyed Saeid Rahimian Koloor ◽

Michal Petrů

Keyword(s):

Boron Nitride ◽

Band Gap ◽

Density Functional ◽

Hexagonal Boron Nitride ◽

Tight Binding ◽

Band Gap Energy ◽

Specific Structure ◽

Partial Substitution ◽

Generalized Gradient ◽

Complete Replacement

The absence of a band gap in graphene is a hindrance to its application in electronic devices. Alternately, the complete replacement of carbon atoms with B and N atoms in graphene structures led to the formation of hexagonal boron nitride (h-BN) and caused the opening of its gap. Now, an exciting possibility is a partial substitution of C atoms with B and N atoms in the graphene structure, which caused the formation of a boron nitride composite with specified stoichiometry. BC2N nanotubes are more stable than other triple compounds due to the existence of a maximum number of B–N and C–C bonds. This paper focused on the nearest neighbor’s tight-binding method to explore the dispersion relation of BC2N, which has no chemical bond between its carbon atoms. More specifically, the band dispersion of this specific structure and the effects of energy hopping in boron–carbon and nitrogen–carbon atoms on the band gap are studied. Besides, the band structure is achieved from density functional theory (DFT) using the generalized gradient approximations (GGA) approximation method. This calculation shows that this specific structure is semimetal, and the band gap energy is 0.167 ev.

Download Full-text

Study of Band Alignment at CBD-CdS/Cu(In1-xGax)Se2 (x = 0.2 - 1.0) Interfaces by Photoemission and Inverse Photoemission Spectroscopy

MRS Proceedings ◽

10.1557/proc-1012-y03-19 ◽

2007 ◽

Vol 1012 ◽

Cited By ~ 5

Author(s):

Shimpei Teshima ◽

Hirotake Kashiwabara ◽

Keimei Masamoto ◽

Kazuya Kikunaga ◽

Kazunori Takeshita ◽

...

Keyword(s):

Band Gap ◽

Conduction Band ◽

Valence Band Maximum ◽

Band Gap Energy ◽

Band Alignment ◽

Photoemission Spectroscopy ◽

Gap Energy ◽

Conduction Band Offset ◽

Inverse Photoemission ◽

Inverse Photoemission Spectroscopy

AbstractDependence of band alignments at interfaces between CdS by chemical bath deposition and Cu(In1-xGax)Se2 by conventional 3-stage co-evaporation on Ga substitution ratio x from 0.2 to 1.0 has been systematically studied by means of photoemission spectroscopy (PES) and inverse photoemission spectroscopy (IPES). For the specimens of the In-rich CIGS, conduction band minimum (CBM) by CIGS was lower than that of CdS. Conduction band offset of them was positive about +0.3 ~ +0.4 eV. Almost flat conduction band alignment was realized at x = 0.4 ~ 0.5. On the other hand, at the interfaces over the Ga-rich CIGS, CBM of CIGS was higher than that of CdS, and CBO became negative. The present study reveals that the decrease of CBO with a rise of x presents over the wide rage of x, which results in the sign change of CBO around 0.4 ~ 0.45. In the Ga-rich interfaces, the minimum of band gap energy, which corresponded to energy spacing between CBM of CdS and valence band maximum of CIGS, was almost identical against the change of band gap energy of CIGS. Additionally, local accumulation of oxygen related impurities was observed at the Ga-rich samples, which might cause the local rise of band edges in central region of the interface.

Download Full-text

Electronic properties of the Sn1−xPbxO alloy and band alignment of the SnO/PbO system: a DFT study

Scientific Reports ◽

10.1038/s41598-020-73703-y ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

N. Kelaidis ◽

S. Bousiadi ◽

M. Zervos ◽

A. Chroneos ◽

N. N. Lathiotakis

Keyword(s):

Band Gap ◽

Electronic Properties ◽

Density Functional ◽

Hydrogen Generation ◽

Valence Band Maximum ◽

Oxide System ◽

Band Alignment ◽

Oxide Thin Film ◽

Ternary Oxide ◽

P Type

Abstract Tin monoxide (SnO) has attracted attention due to its p-type character and capability of ambipolar conductivity when properly doped, properties that are beneficial for the realization of complementary oxide thin film transistors technology, transparent flexible circuits and optoelectronic applications in general. However, its small fundamental band gap (0.7 eV) limits its applications as a solar energy material, therefore tuning its electronic properties is necessary for optimal performance. In this work, we use density functional theory (DFT) calculations to examine the electronic properties of the Sn1−xPbxO ternary oxide system. Alloying with Pb by element substitution increases the band gap of SnO without inducing defect states in the band gap retaining the anti-bonding character of the valence band maximum which is beneficial for p-type conductivity. We also examine the properties of the SnO/PbO heterojunction system in terms of band alignment and the effect of the most common intrinsic defects. A broken gap band alignment for the SnO/PbO heterojunction is calculated, which can be attractive for energy conversion in solar cells, photocatalysis and hydrogen generation.

Download Full-text

First-principles study on the band structure, magnetic and elastic properties of half-metallic Cr2MnAl

Modern Physics Letters B ◽

10.1142/s0217984915501390 ◽

2015 ◽

Vol 29 (24) ◽

pp. 1550139 ◽

Cited By ~ 6

Author(s):

Santao Qi ◽

Chuan-Hui Zhang ◽

Bao Chen ◽

Jiang Shen

Keyword(s):

Band Structure ◽

Band Gap ◽

Elastic Properties ◽

Density Functional ◽

Stable State ◽

Generalized Gradient ◽

Half Metallic ◽

Text Type ◽

Calculation Results ◽

Indirect Band Gap

In this study, we have investigated the structural, electronic, magnetic and elastic properties of the full-Heusler [Formula: see text] alloy in the framework of density functional theory with generalized gradient approximation (GGA). The calculated results showed that [Formula: see text] was stable in ferrimagnetic configuration and crystallized in the [Formula: see text]-type structure. From the band structure and density of states calculation results, we concluded that [Formula: see text] belongs to a kind of half-metallic compound with an indirect band gap of 0.37 eV. Immediately thereafter, we have analyzed the origin of half-metallic band gap. The total magnetic moment of [Formula: see text] at the stable state is [Formula: see text] per formula unit, obeying the Slater–Pauling rule [Formula: see text]. In addition, various mechanical properties have been obtained and discussed based on the three principle elastic tensor elements [Formula: see text] and [Formula: see text] for the first time in the present work. We expect that our calculated results may trigger the application of [Formula: see text] in future spintronics field.

Download Full-text