scholarly journals An Ab initio Study on the Convergence of Electronic Properties of SiC Nanotubes

2013 ◽  
Vol 3 ◽  
pp. 69-73
Author(s):  
Kapil Adhikari ◽  
Asok K. Ray
Keyword(s):  
Silicon Carbide ◽  
Ab Initio ◽  
Electronic Properties ◽  
Density Functional ◽  
National Laboratory ◽  
Basis Sets ◽  
Los Alamos National Laboratory ◽  
Exchange Correlation ◽  
Unit Cells ◽  
Hybrid Density Functional

Ab initio calculations of the electronic structures of silicon carbide (SiC) nanotubes represented by clusters are presented. The nanotube clusters of chiralities (3,3) and (5,5) are studied using the hybrid density functional B3LYP (Becke’s 3-parameter and the Lee-Yang-Parr exchange-correlation) and LANL2DZ (Los Alamos National Laboratory double ?) and 3-21G* basis sets. Evolution of electronic properties of silicon carbide (SiC) nanotubes (3, 3) and (5,5) with their length is discussed. The results suggest that the electronic properties of nanotubes change for short tubes of unit cells with lengths varying from 1 to 5. However, the properties do not seem to change significantly after this. Therefore, an infinite silicon carbide (SiC) nanotube can be approximated by a nanotube cluster of 5 unit cells.The Himalayan PhysicsVol. 3, No. 3, July 2012Page : 69-73

Ab initio study of naphthalene and anthracene elastic properties

2018 ◽  
Vol 29 (03) ◽  
pp. 1850024 ◽  
Author(s):  
Tigran L. Prazyan ◽  
Yuri N. Zhuravlev
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Local Density ◽  
Potential Gradient ◽  
Van Der Waals Interactions ◽  
Acoustic Properties ◽  
Basis Sets ◽  
Hybrid Functional ◽  
Hill Model ◽  
Exchange Correlation

A study of the crystal structure, mechanical and acoustic properties of two [Formula: see text] and [Formula: see text] monoclinic phases of naphthalene and anthracene was performed using ab initio method of linear combination of atomic orbitals (LCAO) and basis sets: C_6-21G*, H_3-1p1G. The method was implemented in the CRYSTAL[Formula: see text]14,[Formula: see text]17 software package using electron density functional theory including van der Waals interactions (DFT-D2 and DFT-D3 (BJ)), in the local density approximation (LDA) with VWN exchange-correlation potential, gradient approximation PBE exchange-correlation functional and B3LYP hybrid functional. The calculated elastic constants for the first time are in moderate agreement with experimental data. Bulk modulus [Formula: see text], shear modulus [Formula: see text], Young’s modulus [Formula: see text] and the Poisson’s ratio [Formula: see text], as well as acoustic properties (average velocity of sound [Formula: see text], the Debye temperature [Formula: see text], and acoustic Grüneisen parameter [Formula: see text]) were obtained using the Voigt–Reuss–Hill model.

Germanene: a new electronic gas sensing material

RSC Advances ◽  
2016 ◽  
Vol 6 (104) ◽  
pp. 102264-102271 ◽  
Author(s):  
Sanjeev K. Gupta ◽  
Deobrat Singh ◽  
Kaptansinh Rajput ◽  
Yogesh Sonvane
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Electronic Properties ◽  
Structural Stability ◽  
Density Functional ◽  
Gas Sensing ◽  
Functional Theory ◽  
Adsorption Characteristics ◽  
Sensing Material ◽  
Gas Molecules

The structural stability and electronic properties of the adsorption characteristics of several toxic gas molecules (NH3, SO2 and NO2) on a germanene monolayer were investigated using density functional theory (DFT) based on an ab initio method.

Quantum-Chemical Ab Initio Calculations on Inda- and Thallabenzene (C5H5In and C5H5Tl) and their Structural Isomers η5-C5H5In and η5-C5H5Tl

2018 ◽  
Vol 71 (3) ◽  
pp. 102
Author(s):  
Emma Persoon ◽  
Yuekui Wang ◽  
Gerhard Raabe
Keyword(s):  
Ab Initio ◽  
Quantum Chemical ◽  
Density Functional ◽  
Single Point ◽  
Normal Modes ◽  
Dft Method ◽  
Basis Sets ◽  
Triplet States ◽  
Structural Isomers ◽  
Td Dft

Quantum-chemical ab initio, time-independent, as well as time-dependent density functional theory (TD-DFT) calculations were performed on the so far elusive heterocycles inda- and thallabenzene (C5H5In and C5H5Tl), employing several different methods (MP2, CISD, CCSD, CCSD(T), BD, BD(T), QCISD, QCISD(T), CASSCF, DFT/B3LYP), effective core potentials, and different basis sets. While calculations on the MP2 level predict the ground states of the title compounds to be singlets with the first triplet states between 13 and 15 kcal mol−1 higher in energy, single point calculations with the QCISD(T), CCSD(T), and BD(T) methods at CCSD-optimized structures result in energy differences between the singlet and the triplet states in the range between 0.3 and 2.1 kcal mol−1 in favour of the triplet states. According to a CASSCF(8,8) calculation the triplets are also more stable by about 2.5–2.9 kcal mol−1. Calculations were also performed for the C5v-symmetric η5 structural isomers (cyclopentadienylindium, CpIn, and cyclopentadienylthallium, CpTl, Cp = C5H5) of the title compounds. At the highest level of theory employed in this study, C5H5In is between 79 and 88 kcal mol−1 higher in energy than CpIn, while this energy difference is even larger for thallabenzene where C5H5Tl is energetically between 94 and 102 kcal mol−1 above CpTl. In addition we report on the UV/vis spectra calculated with a TD-DFT method as well as on the spectra of the normal modes of C5H5In and C5H5Tl. Both types of spectra might facilitate identification of the title compounds eventually formed in photolysis or pyrolysis experiments.

scholarly journals Structural and Electronic Properties of Orthorhombic Phase Bi2Se3 Based On First-Principles Study

2019 ◽  
Vol 16 (2) ◽  
pp. 77 ◽  
Author(s):  
Muhammad Zamir Mohyedin ◽  
Afiq Radzwan ◽  
Mohammad Fariz Mohamad Taib ◽  
Rosnah Zakaria ◽  
Nor Kartini Jaafar ◽  
...  
Keyword(s):  
Electronic Properties ◽  
First Principles ◽  
Density Functional ◽  
Local Density ◽  
Computer Code ◽  
First Principles Calculation ◽  
Generalized Gradient ◽  
Exchange Correlation ◽  
Percentage Difference ◽  
Structural And Electronic Properties

Bi2Se3 is one of the promising materials in thermoelectric devices and very useful out of environmental concern due to its efficiency to perform at room temperature. Based on the first-principles calculation of density functional theory (DFT) by using CASTEP computer code, structural and electronic properties of Bi2Se3 were investigated. The calculation is conducted within the exchange-correlation of local density approximation (LDA) and generalized gradient approximation within the revision of Perdew-Burke-Ernzerhof (GGA-PBE) functional. It was found that the results are consistent with previous works of theoretical study with small percentage difference. LDA exchange-correlation functional method is more accurate and have a better agreement than GGA-PBE to describe the structural properties of Bi2Se3 which consist of lattice parameters. LDA functional also shown more accurate electronic structure of Bi2Se3 that consist of band structure and density of states (DOS) which consistent with most previous theoretical works with small percentage difference. This study proves the reliability of CASTEP computer code and show LDA exchange-correlation functional is more accurate in describing the nature of Bi2Se3 compared to the other functionals.

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