scholarly journals First Principle Study of the Attachment of Graphene onto Different Terminated Diamond (111) Surfaces

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
S. Zhao ◽  
K. Larsson
Keyword(s):  
Density Functional ◽  
Dft Method ◽  
Adhesion Energy ◽  
Van Der Waals Interactions ◽  
Diamond Surface ◽  
Graphene Monolayer ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Aromatic Character ◽  
Finite Band

The adhesion of a graphene monolayer onto terminated or 2x1-reconstructed diamond (111) surfaces has in the present study been theoretically investigated by using a Density Functional Theory (DFT) method. H, F, O, and OH species were used for the surface termination. The generalized gradient spin density approximation (GG(S)A) with the semiempirical dispersion corrections were used in the study of the Van der Waals interactions. There is a weaker interfacial bond (only of type Wan-der-Waals interaction) at a distance around 3 Å (from 2.68 to 3.36 Å ) for the interfacial graphene//diamond systems in the present study. The strongest binding of graphene was obtained for the H-terminated surface, with an adhesion energy of -10.6 eV. In contrast, the weakest binding of graphene was obtained for F-termination (with an adhesion energy of -2.9 eV). For all situations in the present study, the graphene layer was found to retain its aromatic character. In spite of this, a certain degree of electron transfer was observed to take place from graphene to Oontop-, Obridge-, and OH-terminated diamond surface. In addition, graphene attached to Oontop-terminated surface showed a finite band gap.

scholarly journals Effect of Dimensionality on The Electronic Properties of SnSe: A Density Functional Theory Study

2021 ◽  
Vol 32 (2) ◽  
pp. 6-11
Author(s):  
Fatimah Arofiati Noor ◽  
Erik Bhekti Yutomo ◽  
Toto Winata
Keyword(s):  
Density Functional Theory ◽  
Electronic Properties ◽  
Thermoelectric Properties ◽  
Density Functional ◽  
Quantum Confinement Effect ◽  
Dft Method ◽  
Lattice Parameter ◽  
Van Der Waals Interactions ◽  
Generalized Gradient ◽  
Functional Theory

This study investigated the structural and electronic properties of bulk, bilayer, and monolayer SnSe using the density functional theory (DFT) method. We succeeded in calculating the bandgap and identifying accurately the transformation of the band structure from bulk to monolayer systems using generalized gradient approximation. An increase in the lattice parameter a and a decrease in the lattice parameter b were observed when the bulk dimensions were reduced to a monolayer. The reduction of van der Waals interactions when the dimensions of a system are reduced is the main factor that causes changes in lattice parameters. The indirect bandgap of bulk SnSe (0.56 eV, 0.3∆→0.7Σ) becomes wider in the monolayer system (0.94 eV, 0.2∆→0.8Σ). Bandgap widening is predicted due to the emergence of the quantum confinement effect in low-dimensional systems. Furthermore, we found the formation of a quasi-degenerate minimum conduction band in the monolayer SnSe. With the formation of these bands, we predict the monolayer SnSe will have better thermoelectric properties than the bulk or bilayer system. This study provides an in-depth understanding of the electronic structure of SnSe and its correlation to thermoelectric properties.

scholarly journals Density functional theory study of electronic properties of Bi2Se3 and Bi2Te3

2017 ◽  
Vol 12 (3) ◽  
Author(s):  
Abdullahi Lawal ◽  
Amiruddin Shaari
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Topological Insulators ◽  
Van Der Waals Interactions ◽  
Partial Density ◽  
Total Density ◽  
Density Of State ◽  
Generalized Gradient ◽  
Linear Dispersion ◽  
Functional Theory

Topological insulators are layered materials via van der Waals interactions with hexagonal unit cell similar to that of graphene. The exciting features of Bi2Se3 and Bi2Te3 topological insulators their zero band gap surface states exhibiting linear dispersion at the Fermi energy. We present here first principles study pertaining to electronics properties of Bi2Se3 and Bi2Te3 compound with and without spin-orbit interaction using density functional theory (DFT). Total density of state (DOS), partial density of state (PDOS) and band structure where determined by Quantum-Espresso simulation package which uses plane wave basis and pseudopotential for the core electrons, while treating exchange-correlation potential with generalized gradient approximation (GGA). From our computations, the obtained results were found to be consistent with the available experimental results. 

scholarly journals Theoretical study of the band structure of 2H-SiC and 4H-SiC of silicon carbide polytypes

2021 ◽  
Vol 24 (2) ◽  
pp. 23706
Author(s):  
A. V. Sinelnik ◽  
A. V. Semenov
Keyword(s):  
Silicon Carbide ◽  
Band Structure ◽  
Density Functional ◽  
Dft Method ◽  
Generalized Gradient ◽  
Gw Approximation ◽  
Electronic Band ◽  
Functional Theory ◽  
Optimum Approach ◽  
Experimental Values

We have studied the electronic band properties of 2H-SiC and 4H-SiC silicon carbide polytypes. The structures of the electronic bands and density of state (DOS) using ab initio Density Functional Theory (DFT) were calculated for the first Brillouin zone both in the generalized gradient approximation and taking into account quasiparticle effects according to the GW scheme. The calculated bandgaps obtained using the GW approximation Eg2H-SiC = 3.17 eV and Eg4H-SiC = 3.26 eV agree well with experimental values. The shape and values of total DOS are within agreement with calculations performed by other authors. The calculated total energy values for 2H-SiC and 4H-SiC were close, but they satisfy the condition E2H > E4H, which implies that the 4H-SiC structure is more stable than 2H-SiC. Our calculations of the band structure and DOS of 2H-SiC and 4H-SiC by the DFT method showed that the application of the GW approximation is an optimum approach to the study of the electronic structure of 2H-SiC and 4H-SiC polytypes.

scholarly journals Strain Effects on the Electronic and Thermoelectric Properties of n(PbTe)-m(Bi2Te3) System Compounds

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4086
Author(s):  
Weiliang Ma ◽  
Marie-Christine Record ◽  
Jing Tian ◽  
Pascal Boulet
Keyword(s):  
Density Functional ◽  
Lattice Thermal Conductivity ◽  
Compressive Strain ◽  
Van Der Waals Interactions ◽  
Functional Theory ◽  
Band Engineering ◽  
Seebeck Coefficients ◽  
The Density Functional Theory ◽  
P Type ◽  
Narrow Band Gap Semiconductors

Owing to their low lattice thermal conductivity, many compounds of the n(PbTe)-m(Bi2Te3) homologous series have been reported in the literature with thermoelectric (TE) properties that still need improvement. For this purpose, in this work, we have implemented the band engineering approach by applying biaxial tensile and compressive strains using the density functional theory (DFT) on various compounds of this series, namely Bi2Te3, PbBi2Te4, PbBi4Te7 and Pb2Bi2Te5. All the fully relaxed Bi2Te3, PbBi2Te4, PbBi4Te7 and Pb2Bi2Te5 compounds are narrow band-gap semiconductors. When applying strains, a semiconductor-to-metal transition occurs for all the compounds. Within the range of open-gap, the electrical conductivity decreases as the compressive strain increases. We also found that compressive strains cause larger Seebeck coefficients than tensile ones, with the maximum Seebeck coefficient being located at −2%, −6%, −3% and 0% strain for p-type Bi2Te3, PbBi2Te4, PbBi4Te7 and Pb2Bi2Te5, respectively. The use of the quantum theory of atoms in molecules (QTAIM) as a complementary tool has shown that the van der Waals interactions located between the structure slabs evolve with strains as well as the topological properties of Bi2Te3 and PbBi2Te4. This study shows that the TE performance of the n(PbTe)-m(Bi2Te3) compounds is modified under strains.

Understanding the molecular mechanism of the stereoselective conversion of N-trialkylsilyloxy nitronates into bicyclic isoxazoline derivatives

2021 ◽  
Author(s):  
Agnieszka Kącka-Zych ◽  
Radomir Jasinski
Keyword(s):  
Density Functional Theory ◽  
Molecular Mechanism ◽  
Electron Density ◽  
Density Functional ◽  
Dft Method ◽  
Functional Theory ◽  
Molecular Electron ◽  
Molecular Electron Density Theory

Conversion of N-trialkylsilyloxy nitronates into bicyclic isoxazoline derivatives has been explored using Density Functional Theory (DFT) method within the context of the Molecular Electron Density Theory (MEDT) at the B97XD(PCM)/6-311G(d,p)...

scholarly journals Boron-Decorated Pillared Graphene as the Basic Element for Supercapacitors: An Ab Initio Study

2021 ◽  
Vol 11 (8) ◽  
pp. 3496
Author(s):  
Dmitry A. Kolosov ◽  
Olga E. Glukhova
Keyword(s):  
Density Functional ◽  
Dft Method ◽  
Heat Of Formation ◽  
Basic Element ◽  
Supercapacitor Electrode ◽  
Functional Theory ◽  
Icosahedral Clusters ◽  
New Material ◽  
Principle Density Functional Theory ◽  
Specific Quantum

In this work, using the first-principle density functional theory (DFT) method, we study the properties of a new material based on pillared graphene and the icosahedral clusters of boron B12 as a supercapacitor electrode material. The new composite material demonstrates a high specific quantum capacitance, specific charge density, and a negative value of heat of formation, which indicates its efficiency. It is shown that the density of electronic states increases during the addition of clusters, which predictably leads to an increase in the electrode conductivity. We predict that the use of a composite based on pillared graphene and boron will increase the efficiency of existing supercapacitors.

Dissociation of dinitrogen on iron clusters: A detailed study of the Fe16 + N2 case.

2020 ◽  
Author(s):  
Bole Chen ◽  
Gennady L. Gutsev ◽  
Weiguo Sun ◽  
Xiao-Yu Kuang ◽  
Cheng Lu ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Basis Set ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Iron Clusters ◽  
Generalized Gradient Approximation

The coalescence of two Fe8N as well as the structure of the Fe16N2 cluster were studied using density functional theory with the generalized gradient approximation and a basis set of...

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