scholarly journals Poisonous Vapor Adsorption on Pure and Modified Aluminum Nitride Nanosheet for Environmental Safety: A DFT Exploration

2020 ◽  
Vol 12 (23) ◽  
pp. 10097
Author(s):  
Hongni Zhang ◽  
Wenzheng Du ◽  
Tong Zhao ◽  
Rajeev Ahuja ◽  
Zhao Qian
Keyword(s):  
Band Gap ◽  
Adsorption Energy ◽  
Density Functional ◽  
Theoretical Work ◽  
Environmental Safety ◽  
Atomic Scale ◽  
Atomic Structures ◽  
Vapor Sensing ◽  
Two Dimensional Materials ◽  
Si Doped

Through Density Functional Theory (DFT), we have unveiled the atomic structures, adsorption characteristics and electronic structures of the poisonous and explosive vapor, m-dinitrobenzene (m-DNB), on pure, defective and various doped AlN nanosheets from a physical perspective. It is found that the adsorption energy, band gap change and sensitivity to the vapor are significantly increased through atomic-scale modification of the nanosheet. The AlN monolayer with Al-N divacancy has the largest adsorption energy and has potential to be utilized as adsorption or filtration materials for m-DNB vapor. The Si-doped AlN nanosheet possesses a much larger band gap change (−0.691 eV) than the pure nanosheet (−0.092 eV) after adsorption and has a moderate adsorption energy, which could be candidate material for explosive vapor sensing. This theoretical work is proposed to provide guidance and clue for experimentalists to develop more effective two-dimensional materials for environmental safety and sustainability.

Ab-Initio Theory of Initial Oxidation of Silicon (001) Surfaces

1997 ◽  
Vol 492 ◽  
Author(s):  
N. A. Modine ◽  
G. Zumbach ◽  
E. Kaxiras
Keyword(s):  
Oxygen Atom ◽  
Photoelectron Spectroscopy ◽  
Density Functional ◽  
Experimental Studies ◽  
Theoretical Work ◽  
Real Space ◽  
Initial Oxidation ◽  
Atomic Structures ◽  
Ab Initio Theory ◽  
Initial Oxygen

ABSTRACTThe oxidation of the Si(001) surface is an important process on both technological and theoretical grounds. Experimental studies have not provided a clear picture of even the relevant atomic structures during the initial stages of oxidation, while previous theoretical studies of these processes have yielded contradictory results. Using careful first principles total-energy calculations based on density functional theory, we study several mechanisms of incorporating a sub-monolayer coverage of oxygen into the characteristic p(2 × 1) dimer reconstruction of the Si(001) surface. Our recently developed Adaptive Coordinate Real-space Electronic Structure (ACRES) method allows us to obtain results that are adequately converged with respect to the numerous computational parameters associated with this difficult system. We compare our results with previous theoretical work and propose a physically motivated two step pathway for the initial incorporation of an oxygen atom into the dimerized surface. Based on our results, we can explain what formerly appeared to be puzzling Ultraviolet Photoelectron Spectroscopy measurements which indicated that each initial oxygen atom saturates two surface dangling bonds.

scholarly journals Stabilizing hidden room-temperature ferroelectricity via a metastable atomic distortion pattern

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Jeong Rae Kim ◽  
Jinhyuk Jang ◽  
Kyoung-June Go ◽  
Se Young Park ◽  
Chang Jae Roh ◽  
...  
Keyword(s):  
Density Functional ◽  
Room Temperature ◽  
Deep Neural Network ◽  
Close Correlation ◽  
Perovskite Oxides ◽  
Atomic Scale ◽  
Neural Network Analysis ◽  
Functional Theory ◽  
Atomic Structures ◽  
Equilibrium Pattern

Abstract Nonequilibrium atomic structures can host exotic and technologically relevant properties in otherwise conventional materials. Oxygen octahedral rotation forms a fundamental atomic distortion in perovskite oxides, but only a few patterns are predominantly present at equilibrium. This has restricted the range of possible properties and functions of perovskite oxides, necessitating the utilization of nonequilibrium patterns of octahedral rotation. Here, we report that a designed metastable pattern of octahedral rotation leads to robust room-temperature ferroelectricity in CaTiO3, which is otherwise nonpolar down to 0 K. Guided by density-functional theory, we selectively stabilize the metastable pattern, distinct from the equilibrium pattern and cooperative with ferroelectricity, in heteroepitaxial films of CaTiO3. Atomic-scale imaging combined with deep neural network analysis confirms a close correlation between the metastable pattern and ferroelectricity. This work reveals a hidden but functional pattern of oxygen octahedral rotation and opens avenues for designing multifunctional materials.

A DFT study of pressure-induced phase transitions, structural and electronic properties of Cu2ZnSnS4

2016 ◽  
Vol 30 (16) ◽  
pp. 1650176 ◽  
Author(s):  
Yifen Zhao ◽  
Decong Li ◽  
Zuming Liu
Keyword(s):  
Phase Transitions ◽  
Band Gap ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Theoretical Work ◽  
Functional Theory ◽  
Phase Transition Pressure ◽  
Structural And Electronic Properties ◽  
Direct Band

The structural properties, phase transitions, and electronic structures of Cu2ZnSnS4 (CZTS) in the three structures have been researched using the first-principles density functional theory (DFT). The results indicate that the energies of stannite (ST) and pre-mixed Cu–Au (PMCA) CZTS are higher than those of kesterite (KS) CZTS, indicating that the KS CZTS is more stable. We found the phase transition pressure between the KS and ST structures of CZTS is about 32 GPa. Moreover, for KS- and PMCA-CZTS, there exists in the mischcrystal phase between 52 GPa and 65 GPa. The band structures show that the KS- and ST-CZTS are direct band gap semiconductors. The band gaps of three-type CZTS increase with increasing pressure, and the maximum band gap of KS and ST structures for CZTS occurs at 50 GPa. However, PMCA CZTS possesses metal property. Furthermore, the PMCA CZTS translates from metal to the indirect semiconductor with increasing pressure. The results play an important role in future experimental and theoretical work for CZTS materials.

Laser Irradiation of Atomic Chains: A Show-Case Study Based on the Density Functional Theory

2006 ◽  
Vol 960 ◽  
Author(s):  
Anna M. Mazzone ◽  
Marco Bianconi
Keyword(s):  
Density Functional Theory ◽  
Laser Irradiation ◽  
Density Functional ◽  
Laser Pulses ◽  
Chain Structure ◽  
Atomic Scale ◽  
Functional Theory ◽  
Atomic Structures ◽  
The Density Functional Theory ◽  
Atomic Chains

ABSTRACTThis study is motivated by recent applications of short laser pulses to the manipulation of atomic structures at the atomic scale and is based on the Density Functional Theory. The structures considered are linear monoatomic chains, formed by covalent and metallic atoms, and the calculations illustrate their evolution under laser irradiation. The calaculations show that the modification of the chain structure spans from a slight relaxation of the interatomic distances to fragmentation and illustrate the times and energies needed to induce those changes.

Largest Band Gap of All Single Walled Carbon Nanotubes

2003 ◽  
Vol 772 ◽  
Author(s):  
I. Cabria ◽  
J. W. Mintmire ◽  
C. T. White
Keyword(s):  
Carbon Nanotubes ◽  
Band Gap ◽  
Density Functional ◽  
Local Density ◽  
Tight Binding ◽  
Single Walled Carbon Nanotubes ◽  
Theoretical Work ◽  
First Principles Calculations ◽  
Single Walled Carbon ◽  
Walled Carbon Nanotubes

AbstractSingle walled carbon nanotubes, SWNTs, are either semiconducting, metallic, or quasimetallic. Early theoretical work based on tight-binding models predicted that the band gap of semiconducting carbon nanotubes should increase with decreasing radius and this picture was later confirmed by experiment. However, local-density functional calculations indicate that these models are not accurate for narrow carbon nanotubes, where the effects of curvature can convert nanotubes expected to be semiconductors to metals. This raises the question, what is the largest semiconducting band gap possible in a SWNT? We present results from first-principles calculations for a range of carbon nanotubes with radii between 0.15 and 1 nm. These results indicate that the (4,3) carbon nanotube has the largest band gap of all SWNTs.

Electronic theory study on the electronic structure and optical properties of S-adsorbed graphene

2018 ◽  
Vol 32 (27) ◽  
pp. 1850324 ◽  
Author(s):  
Lin Wei ◽  
Guili Liu ◽  
Dazhi Fan ◽  
Guoying Zhang
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Band Structure ◽  
Band Gap ◽  
Adsorption Energy ◽  
Density Functional ◽  
Twist Angle ◽  
Torsional Angle ◽  
Torsional Deformation ◽  
The Stability

The effects of coverage and torsional angle on the stability, electronic structure and optical properties of S-absorbed graphene system are studied by using density functional theory based on the first-principles. The adsorption energy, band structure, light absorption coefficient and reflectivity are calculated through it. In the current research area, it is found that the coverage has little effect on the adsorption of the system, but the C atoms are pulled up, the graphene plane is distorted, and the band gap of the graphene is opened, which changes graphene from quasi-metal to semiconductors. S-adsorbed graphene system has a blueshift relative to the intrinsic graphene, and the degree of blueshift increases with the increase of coverage. The reflectivity of the system is higher than that of the unabsorbed S atom system. Torsional deformation has a large effect on its band gap. It makes the adsorption system reduce the adsorption energy and the stability. The band structure shows that the band gap decreases as the twist angle increases. The twisted S-adsorbed graphene system shows a slight redshift, and the degree of redshift increases with the angle. The maximum reflectance of the S-adsorbed graphene system with torsional deformation is stronger than that of the untwisted system.

Quasiperiodic interfaces: HREM observations of grain and phase boundaries

1990 ◽  
Vol 48 (4) ◽  
pp. 332-333
Author(s):  
K. L. Merkle
Keyword(s):  
Atomic Structure ◽  
Direct Determination ◽  
Lattice Parameter ◽  
Atomic Scale ◽  
Misfit Dislocations ◽  
Oxide Systems ◽  
Atomic Structures ◽  
Periodic Arrays ◽  
Parameter Ratio ◽  
Metal Metal

The atomic structures of internal interfaces have recently received considerable attention, not only because of their importance in determining many materials properties, but also because the atomic structure of many interfaces has become accessible to direct atomic-scale observation by modem HREM instruments. In this communication, several interface structures are examined by HREM in terms of their structural periodicities along the interface.It is well known that heterophase boundaries are generally formed by two low-index planes. Often, as is the case in many fcc metal/metal and metal/metal-oxide systems, low energy boundaries form in the cube-on-cube orientation on (111). Since the lattice parameter ratio between the two materials generally is not a rational number, such boundaries are incommensurate. Therefore, even though periodic arrays of misfit dislocations have been observed by TEM techniques for numerous heterophase systems, such interfaces are quasiperiodic on an atomic scale. Interfaces with misfit dislocations are semicoherent, where atomically well-matched regions alternate with regions of misfit. When the misfit is large, misfit localization is often difficult to detect, and direct determination of the atomic structure of the interface from HREM alone, may not be possible.

Efficient Prediction of Structural and Electronic Properties of Hybrid 2D Materials Using DFT and Machine Learning

2018 ◽  
Author(s):  
Sherif Tawfik ◽  
Olexandr Isayev ◽  
Catherine Stampfl ◽  
Joseph Shapter ◽  
David Winkler ◽  
...  
Keyword(s):  
Machine Learning ◽  
Band Gap ◽  
Density Functional ◽  
2D Materials ◽  
Van Der Waals ◽  
Building Blocks ◽  
Machine Learning Techniques ◽  
Interlayer Distance ◽  
Computational Screening ◽  
Wide Range

Materials constructed from different van der Waals two-dimensional (2D) heterostructures offer a wide range of benefits, but these systems have been little studied because of their experimental and computational complextiy, and because of the very large number of possible combinations of 2D building blocks. The simulation of the interface between two different 2D materials is computationally challenging due to the lattice mismatch problem, which sometimes necessitates the creation of very large simulation cells for performing density-functional theory (DFT) calculations. Here we use a combination of DFT, linear regression and machine learning techniques in order to rapidly determine the interlayer distance between two different 2D heterostructures that are stacked in a bilayer heterostructure, as well as the band gap of the bilayer. Our work provides an excellent proof of concept by quickly and accurately predicting a structural property (the interlayer distance) and an electronic property (the band gap) for a large number of hybrid 2D materials. This work paves the way for rapid computational screening of the vast parameter space of van der Waals heterostructures to identify new hybrid materials with useful and interesting properties.

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