ELECTRONIC STRUCTURE OF GRAPHENE NANORIBBONS SUBJECTED TO TWIST AND NONUNIFORM STRAIN

2011 ◽  
Vol 20 (01) ◽  
pp. 153-160 ◽  
Author(s):  
A. DOBRINSKY ◽  
A. SADRZADEH ◽  
B. I. YAKOBSON ◽  
J. XU
Keyword(s):  
Band Gap ◽  
Density Functional ◽  
Graphene Nanoribbons ◽  
Tight Binding ◽  
Tight Binding Approximation ◽  
Functional Theory ◽  
Gap Opening ◽  
Gap Creation ◽  
Band Gap Modulation ◽  
Twisted Graphene

Graphene nanoribbons exhibit band gap modulation when subjected to strain. While band gap creation has been theoretically investigated for uniaxial strains, other deformations such as nanoribbon twist have not been considered. Our main objective in this paper is to explore band gap opening in twisted graphene nanoribbons that have metallic properties under tight-binding approximation. While simple considerations based on the Hückel model allow to conclude that zigzag graphene nanoribbons exhibit no band gap when subjected to twist, the Hückel model overall may be inaccurate for band gap prediction in metallic nanoribbons. We utilize Density Functional Theory Tight-Binding Approximation together with a requirement that energy of twisted nanoribbons is minimized to evaluate band gap of metalic armchair nanoribbons. Besides considering twisting deformations, we also explore the possibility of creating band gap when graphene nanoribbons are subject to inhomogeneous deformation such as sinusoidal deformations.

Graphene-Based Sensors for Monitoring Strain

2013 ◽  
Vol 3 (1) ◽  
pp. 74-83
Author(s):  
M. Mirnezhad ◽  
R. Ansari ◽  
H. Rouhi ◽  
M. Faghihnasiri
Keyword(s):  
Fermi Level ◽  
Band Gap ◽  
Strain Distribution ◽  
Density Functional ◽  
Tight Binding ◽  
Density Functional Theory Calculations ◽  
Generalized Gradient ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Gap Opening

The application of graphene as a nanosensor in measuring strain through its band structure around the Fermi level is investigated in this paper. The mechanical properties of graphene as well as its electronic structure are determined by using the density functional theory calculations within the framework of generalized gradient approximation. In the case of electronic properties, the simulations are applied for symmetrical and asymmetrical strain distributions in elastic range; also the tight-binding approach is implemented to verify the results. It is indicated that the energy band gap does not change with the symmetrical strain distribution but depend on the asymmetric strain distribution, increasing strain leads to band gap opening around the Fermi level.

Graphene-Based Sensors for Monitoring Strain

2014 ◽  
pp. 602-611
Author(s):  
M. Mirnezhad ◽  
R. Ansari ◽  
H. Rouhi ◽  
M. Faghihnasiri
Keyword(s):  
Fermi Level ◽  
Band Gap ◽  
Strain Distribution ◽  
Density Functional ◽  
Tight Binding ◽  
Density Functional Theory Calculations ◽  
Generalized Gradient ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Gap Opening

The application of graphene as a nanosensor in measuring strain through its band structure around the Fermi level is investigated in this paper. The mechanical properties of graphene as well as its electronic structure are determined by using the density functional theory calculations within the framework of generalized gradient approximation. In the case of electronic properties, the simulations are applied for symmetrical and asymmetrical strain distributions in elastic range; also the tight-binding approach is implemented to verify the results. It is indicated that the energy band gap does not change with the symmetrical strain distribution but depend on the asymmetric strain distribution, increasing strain leads to band gap opening around the Fermi level.

scholarly journals Hydration Dependent Band Gap Tunability of Self-Assembled Phenylalanine-Tryptophan Nanotubes

2020 ◽  
Author(s):  
Hugo Souza ◽  
Antonio Chaves Neto ◽  
Francisco Sousa ◽  
Rodrigo Amorim ◽  
Alexandre Reily Rocha ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Band Gap ◽  
Electronic Properties ◽  
Building Block ◽  
Density Functional ◽  
Tight Binding ◽  
Water Molecules ◽  
Confined Water ◽  
Functional Theory ◽  
Tight Binding Method

In this work, we investigate the effects of building block separation of Phenylalanine-Tryptophan nanotube induced by the confined water molecules on the electronic properties using density-functional theory based tight-binding method. <div><br></div>

Lattice Dynamics of Graphene Nanoribbons under Twisting

2021 ◽  
Author(s):  
Zhao Liu ◽  
Zhen Zhang ◽  
Hui-Yan Zhao ◽  
Jing Wang ◽  
Ying Liu
Keyword(s):  
Thermal Conductivity ◽  
Lattice Dynamics ◽  
Density Functional ◽  
Lattice Thermal Conductivity ◽  
Graphene Nanoribbons ◽  
Tight Binding ◽  
Tight Binding Method ◽  
Twisted Graphene

In this communication, we investigate the lattice dynamics of twisted graphene nanoribbons utilizing the density-functional tight-binding method based on screw symmetry and report the reduced lattice thermal conductivity due to...

scholarly journals Modulating band gap of C4NP-h2D crystal nanoribbons and nanotubes under elastic strain

RSC Advances ◽  
2017 ◽  
Vol 7 (65) ◽  
pp. 41084-41090 ◽  
Author(s):  
Shengqian Ma ◽  
Weishun Ma ◽  
Feng Li ◽  
Mei Zhu ◽  
Jiguo Geng ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Band Gap ◽  
Elastic Strain ◽  
Density Functional ◽  
Functional Theory ◽  
Band Gap Modulation

Using Density Functional Theory (DFT), band-gap modulation of C4NP-h2D nanoribbons and nanotubes under elastic strain is investigated in detail in this paper.

scholarly journals Even–odd conductance effect in graphene nanoribbons induced by edge functionalization with aromatic molecules: basis for novel chemosensors

2020 ◽  
Vol 135 (8) ◽  
Author(s):  
Kristiāns Čerņevičs ◽  
Michele Pizzochero ◽  
Oleg V. Yazyev
Keyword(s):  
Density Functional ◽  
Nearest Neighbor ◽  
Graphene Nanoribbons ◽  
Energy Levels ◽  
Tight Binding ◽  
Density Functional Theory Calculations ◽  
Aromatic Rings ◽  
Functional Theory ◽  
Aromatic Molecules ◽  
Physical Effects

AbstractWe theoretically investigate the electron transport in armchair and zigzag graphene nanoribbons (GNRs) chemically functionalized with p-polyphenyl and polyacene groups of increasing length. Our nearest-neighbor tight-binding calculations indicate that, depending on whether the number of aromatic rings in the functional group is even or odd, the resulting conductance at energies matching the energy levels of the corresponding isolated molecule is either unaffected or reduced by exactly one quantum as compared to the pristine GNR, respectively. Such an even–odd effect is shown to originate from a subtle interplay between the electronic states of the guest molecule that are spatially localized on the binding sites and those of the host nanoribbon. We next generalize our findings by employing more accurate tight-binding Hamiltonians along with density-functional theory calculations and critically discuss the robustness of the observed physical effects against the level of theory adopted. Our work offers a comprehensive understanding of the influence of aromatic molecules bound to the edge of graphene nanoribbons on their electronic transport properties, an issue which is instrumental to the prospective realization of graphene-based chemosensors.

scholarly journals Hydration Dependent Band Gap Tunability of Self-Assembled Phenylalanine-Tryptophan Nanotubes

2020 ◽  
Author(s):  
Hugo Souza ◽  
Antonio Chaves Neto ◽  
Francisco Sousa ◽  
Rodrigo Amorim ◽  
Alexandre Reily Rocha ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Band Gap ◽  
Electronic Properties ◽  
Building Block ◽  
Density Functional ◽  
Tight Binding ◽  
Water Molecules ◽  
Confined Water ◽  
Functional Theory ◽  
Tight Binding Method

In this work, we investigate the effects of building block separation of Phenylalanine-Tryptophan nanotube induced by the confined water molecules on the electronic properties using density-functional theory based tight-binding method. <div><br></div>

scholarly journals STUDY OF TiO2 NANOPARTICLES’ STRUCTURE USING DENSITY FUNCTIONAL THEORY BASED TIGHT BINDING METHOD

2019 ◽  
Vol 1 (27) ◽  
pp. 79-85
Author(s):  
Hung Thanh Phan
Keyword(s):  
Density Functional Theory ◽  
Band Gap ◽  
Tio2 Nanoparticles ◽  
Energy Band ◽  
Density Functional ◽  
Anatase Phase ◽  
Tight Binding ◽  
Energy Band Gap ◽  
Functional Theory ◽  
Practical Applications

The different structure and size of TiO2 nanoparticles ranging from 0.8 nm to 2.7 nm with two different phases of anatase and rutile were studied by Density  Functional theory based Tight Binding (DFTB) method. The results showed that the stability of the rutile phase was better than that of the anatase phase. Based on calculation of the electronic properties of particles, the energy band gap of rutile particles was comparable to that of bulk structure. In contrast, the energy band gap of the anatase changed irregularly. Moreover, the formation energy that was used for forming the particles was inversely proportional to their size based on computation of energy. The results provided useful instructions for practical applications in fabrication of TiO2 nanoparticles.

Negative Cauchy Pressure within the Tight-Binding Approximation

1997 ◽  
Vol 491 ◽  
Author(s):  
D. Nguyen-Maxh ◽  
D. G. Pettifor ◽  
S. Znam ◽  
V. Vitek
Keyword(s):  
Density Functional ◽  
Functional Form ◽  
Tight Binding ◽  
Embedded Atom Method ◽  
Tight Binding Approximation ◽  
Functional Theory ◽  
Cubic Metals ◽  
Embedded Atom ◽  
Cauchy Pressure ◽  
Environment Dependence

ABSTRACTIt is well-known that the Embedded Atom Method (EAM) predicts positive Cauchy pressures for cubic metals if physically-motivated embedding functions are used. Supris-ingly, even if the angular character of the covalent bonding is included within an orthorgonal or non-orthorgonal Tight-Binding (TB) description, the Cauchy pressure for most elemental and binary metallic systems remains positive. We describe the results of a detailed breakdown of the different contributions to the Cauchy pressure within the Harris-Foulkes approximation (HFA) to density functional theory. We show that negative values of the Cauchy pressure for both elemental transition metals such as Ir and binary intermetallics such as Ti3Al, TiAl and TiAl3 are well reproduced by the HFA. We argue that the negative Cauchy pressure (NCP) arises namely from the environment dependence of the local TB orbitals which leads to both environment-dependent bonding integrals and overlap repulsion. We discuss a particular functional form for overlap repulsion which leads to NCP and compare it with different fitting schemes proposed recently in TB theory.

scholarly journals A theoretical study of (9, 0) Singlewalled Carbon Nanotubes using quantum mechanical techniques

2021 ◽  
Vol 4 (1) ◽  
pp. 10
Author(s):  
Deepa Sharma ◽  
Neena Jaggi
Keyword(s):  
Thermodynamic Properties ◽  
Band Gap ◽  
Density Functional ◽  
Tight Binding ◽  
Finite Energy ◽  
Quantum Mechanical ◽  
Simulation Studies ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Material Studio

First principles simulation studies using the density functional theory have been performed on (9, 0) Zigzag Singlewalled Carbon Nanotube (SWCNT) to investigate its electronic, optical and thermodynamic properties using CASTEP (Cambridge Sequential Total Energy Package) and DFTB (Density Functional based Tight Binding) modules of the Material Studio Software version 7.0. Various functionals and sub-functionals available in the CASTEP Module (using Pulay Density Mixing treatment of electrons) and various eigen-solvers and smearing schemes available in the DFTB module (using smart algorithm) have been tried out to chalk out the electronic structure. The analytically deduced values of the band gap obtained were compared with the experimentally determined value reported in the literature. By comparison, combination of Anderson smearing scheme and standard diaogonalizer produced best results in DFTB module while in the CASTEP module, GGA (General Gradient approximation) functional with RPBE (Revised-perdew-Burke-Ernzerh) as Sub-functional was found to be the most consistent. These optimized parameters were then used to determine various electronic, optical and thermodynamic properties of (9, 0) Singlewalled Nanotube. (9, 0) Singlewalled Nanotube, which is extensively being used for sensing NH3, CH4 & NO2, has been picked up in particular as it is reported to exhibit a finite energy band gap in contrast to its expected metallic nature. The study is of utmost significance as it not only probes and validates the simulation route for predicting suitable properties of nanomaterials but also throws light on the comparative efficacy of the different approximation and rationalization quantum mechanical techniques used in simulation studies.

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