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.

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

A theoretical study of the 77Se NMR and vibrational spectroscopic properties of SenS8–n ring molecules

2002 ◽  
Vol 80 (11) ◽  
pp. 1435-1443 ◽  
Author(s):  
J Komulainen ◽  
R S Laitinen ◽  
R J Suontamo
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Chemical Shifts ◽  
Atomic Orbital ◽  
Geometry Optimization ◽  
Spectroscopic Properties ◽  
Basis Sets ◽  
Orbital Method ◽  
Hybrid Functional ◽  
Ring Molecules

The structures and spectroscopic properties of SenS8–n ring molecules have been studied by the use of ab initio molecular orbital techniques and density functional techniques involving Stuttgart relativistic large core effective core potential approximation with double zeta basis sets for valence orbitals augmented by two polarization functions for both sulfur and selenium. Full geometry optimizations have been carried out for all 30 isomers at the Hartree-Fock level of theory. The optimized geometries and the calculated fundamental vibrations and Raman intensities of the SenS8–n molecules agree closely with experimental information where available. The nuclear magnetic shielding tensor calculations have been carried out by the Gauge-independent atomic orbital method at the DFT level using Becke's three-parameter hybrid functional with Perdew/Wang 91 correlation. The isotropic shielding tensors correlate well with the observed chemical shift data. The calculated chemical shifts provide a definite assignment of the observed 77Se NMR spectroscopic data and can be used in the prediction of the chemical shifts of unknown SenS8–n ring molecules.Key words: selenium sulfides, ab initio, DFT, effective core potentials, geometry optimization, energetics, fundamental vibrations, 77Se chemical shifts.

Structure and Stability of Grain Boundaries in Molybdenum with Segregated Carbon Impurities

1999 ◽  
Vol 578 ◽  
Author(s):  
R. Janisch ◽  
T. Ochs ◽  
A. Merkle ◽  
C. Elsässer
Keyword(s):  
Ab Initio ◽  
Grain Boundaries ◽  
Density Functional ◽  
Local Density ◽  
Structural Parameters ◽  
Carbide Phases ◽  
Carbon Impurities ◽  
Transmission Electron ◽  
Local Density Functional Theory ◽  
Symmetrical Tilt

AbstractThe segregation of interstitial impurities to symmetrical tilt grain boundaries (STGB) in bodycentered cubic transition metals is studied by means of ab-initio electronic-structure calculations based on the local density functional theory (LDFT). Segregation energies as well as changes in atomic and electronic structures at the ΣE5 (310) [001] STGB in Mo caused by segregated interstitial C atoms are investigated. The results are compared to LDFT data obtained previously for the pure Σ5 (310) [001] STGB in Mo. Energetic stabilities and structural parameters calculated ab initio for several crystalline Molybdenum Carbide phases with cubic, tetragonal or hexagonal symmetries and different compositions, MoCx, are reported and compared to recent high-resolution transmission electron microscopy (HRTEM) observations of MoCx, intergranular films and precipitates formed by C segregation to a Σ5 (310) [001] STGB in a Mo bicrystal.

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.

scholarly journals Ab initio thermodynamics of liquid and solid water

2019 ◽  
Vol 116 (4) ◽  
pp. 1110-1115 ◽  
Author(s):  
Bingqing Cheng ◽  
Edgar A. Engel ◽  
Jörg Behler ◽  
Christoph Dellago ◽  
Michele Ceriotti
Keyword(s):  
Machine Learning ◽  
Thermodynamic Properties ◽  
Ab Initio ◽  
Density Functional ◽  
Machine Learning Techniques ◽  
Intermediate Step ◽  
Hybrid Functional ◽  
Learning Techniques ◽  
The Stability ◽  
Comprehensive Framework

Thermodynamic properties of liquid water as well as hexagonal (Ih) and cubic (Ic) ice are predicted based on density functional theory at the hybrid-functional level, rigorously taking into account quantum nuclear motion, anharmonic fluctuations, and proton disorder. This is made possible by combining advanced free-energy methods and state-of-the-art machine-learning techniques. The ab initio description leads to structural properties in excellent agreement with experiments and reliable estimates of the melting points of light and heavy water. We observe that nuclear-quantum effects contribute a crucial 0.2 meV/H2O to the stability of ice Ih, making it more stable than ice Ic. Our computational approach is general and transferable, providing a comprehensive framework for quantitative predictions of ab initio thermodynamic properties using machine-learning potentials as an intermediate step.

AB-INITIO MOLECULAR DYNAMICS IN THE FULL-POTENTIAL LMTO METHOD: DERIVATION OF A PRACTICAL FORCE THEOREM

1993 ◽  
Vol 07 (01n03) ◽  
pp. 262-265 ◽  
Author(s):  
M. METHFESSEL ◽  
M. VAN SCHILFGAARDE
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Local Density ◽  
Basis Set ◽  
Ab Initio Molecular Dynamics ◽  
Basis Sets ◽  
Full Potential ◽  
Major Advance ◽  
First Results ◽  
Lmto Method

A major advance in electronic structure calculations was the combination of local-density techniques with molecular dynamics by Car and Parrinello seven years ago. Unfortunately, application of the Car-Parrinello scheme has been limited essentially to sp materials because only in the plane-wave pseudopotential method forces are trivial to calculate. We present a systematic approach to derive force theorems with desired characteristics within complicated basis sets, which are applicable to all elements of the periodic table equally well. Application to the LMTO basis set yields an accurate force theorem, quite distinct from the Hellman-Feynman form, which is exceptionally insensitive to errors in the trial density. The forces were implemented in a new full-potential LMTO method which is suited to arbitrary geometries. First results for ab-initio molecular dynamics and simulated annealing runs are shown for some random small molecules and small clusters of silver atoms.

First Principles Calculations for Metal/Ceramic Interfaces

1994 ◽  
Vol 357 ◽  
Author(s):  
M. W. Finnis ◽  
C. Kruse ◽  
U. SchÖnberger
Keyword(s):  
Electronic Structure ◽  
High Resolution ◽  
Ab Initio ◽  
First Principles ◽  
Density Functional ◽  
Local Density ◽  
Work Of Adhesion ◽  
First Principles Calculations ◽  
Resolution Electron ◽  
Metal Ceramic

AbstractWe discuss the recent first principles calculations of the properties of interfaces between metals and oxides. This type of calculation is parameter-free, and exploits the density functional theory in the local density approximation to obtain the electronic structure of the system. At the same time the equilibrium atomic structure is sought, which minimises the excess energy of the interface. Up to now calculations of this type have been made for a few model interfaces which are atomically coherent, that is with commensurate lattices. Examples are Ag/MgO and Nb/Al2O3. In these cases it has been possible to predict the structures observed by high resolution electron microscopy. The calculations are actually made in a supercell geometry, in which there are alternating nanolayers of metal and ceramic. Because of the effectiveness of metallic screening in particular, the interfaces between the nanolayers do not interfere much with each other.Besides the electronic structure of the interface, such calculations have provided values of the ideal work of adhesion. Electrostatic image forces in conjunction with the elementary ionic model provide a simple framework for understanding the results.An important role of such calculations is to develop intuition about the nature of the bonding, including the effects of charge transfer, which has formerly only been described in an empirical way. It may then be possible to build atomistic models of the metal/ceramic interaction which have a sound physical basis and can be calibrated against ab initio results. Simpler models are necessary if larger systems, including misfit dislocations and other defects, are to be simulated, with a view to understanding the atomic processes of growth and failure. Another area in which ab initio calculations can be expected to contribute is in the chemistry of impurity segregation and its effect at interfaces. Such theoretical tools are a natural partner to the experimental technique of high resolution electron energy loss spectroscopy for studying the local chemical environment at an interface.

Sign in / Sign up

Export Citation Format

Share Document