Structural and Electronic Properties of a-Gaas: A Tight-Binding–Molecular-Dynamics–Art Simulation

1997 ◽  
Vol 491 ◽  
Author(s):  
Laurent J. Lewis ◽  
Normand Mousseau
Keyword(s):  
Molecular Dynamics ◽  
Mechanical Model ◽  
Tight Binding ◽  
Structural Models ◽  
Type Model ◽  
Low Density ◽  
Needed Information ◽  
Structural And Electronic Properties ◽  
Dynamical Properties ◽  
Tetrahedral Semiconductors

ABSTRACTBy combining tight-binding (TB) molecular dynamics (MD) with the recently-proposed activation-relaxation technique (ART), we have constructed structural models of a-GaAs and a-Si of an unprecedented level of quality: the models are almost perfectly four-fold coordinated and, in the case of a-GaAs, exhibit a remarkably low density of homopolar bonds. In particular, the models are superior to structures obtained using melt-and-quench TB-MD or quantum MD. We find that a-Si is best described by a Polk-type model, while a-GaAs resembles closely the mechanical model proposed by Connell and Temkin, which is free of wrong bonds. In this paper, the structural, electronic, and dynamical properties of a-GaAs based on this approach will be reviewed, and compared to experiment and other structural models. Our study provides much-needed information on the intermediate-range topology of amorphous tetrahedral semiconductors; in particular, we will see that the differences between the Polk and Connell-Temkin models, while real, are difficult to extract from experiment, thus emphasising the need for realistic computer models.

New Approaches to Molecular Dynamics Simulations of a-Si:H

1994 ◽  
Vol 336 ◽  
Author(s):  
Qiming Li ◽  
R. Biswas ◽  
C.M. Soukoulis
Keyword(s):  
Molecular Dynamics ◽  
Tight Binding ◽  
New Physics ◽  
Quantum Mechanical ◽  
Mechanical Forces ◽  
Electronic Effects ◽  
Structural And Electronic Properties ◽  
Charge States ◽  
Dynamics Simulations ◽  
Formation Energies

ABSTRACTA new tight-binding molecular dynamics approach for Si-H systems is developed using the valence orbitale of Si and H for calculation of atomic forces. Previous tight-binding models are not able to describe formation energies of different charge states of H in c-Si and new physics is introduced in our model to describe both effects of charge transfer and varying atomic environments. The Si-H Model was developed by fitting to silane, and ensuring that the formation energies of different charge states of H in c-Si were correctly described. This new model also describes well vibrational properties of SiHn configurations, and the structural and electronic properties of a-Si:H Models. The new molecular dynamics utilizes quantum mechanical forces, incorporating important electronic effects, and is robust enough to simulate hundreds of atoms as would be needed in realistic a-Si:H systems.

scholarly journals Dynamical properties of Au from tight-binding molecular-dynamics simulations

2001 ◽  
Vol 63 (19) ◽  
Author(s):  
F. Kirchhoff ◽  
M. J. Mehl ◽  
N. I. Papanicolaou ◽  
D. A. Papaconstantopoulos ◽  
F. S. Khan
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Tight Binding ◽  
Dynamical Properties ◽  
Dynamics Simulations

Structural and Electronic Properties of Damaged Fullerite Crystals

1994 ◽  
Vol 359 ◽  
Author(s):  
M. Manfredini ◽  
S. Serra ◽  
L. Colombo ◽  
P. Milani
Keyword(s):  
Electronic Properties ◽  
Tight Binding ◽  
Fullerene Cage ◽  
Low Density ◽  
High Fluence ◽  
Structural And Electronic Properties ◽  
Medium Range ◽  
Dynamics Calculation ◽  
Irradiation Process

ABSTRACTA structural tranfsormation of C60 crystals has been induced by high fluence laser irradiation under various chemical environments. The role of oxygen in driving fullerene cage opening reactions is investigated. The resulting material, showing features typical of low density amorphous carbon, has been characterized by Raman spectroscopy. In order to provide an atomistic model of the damaged sample, we have simulated the irradiation process by a tight binding molecular dynamics calculation on a 240-atoms system. We have carefully investigated the structural and electronic properties. In particular, the short- and medium-range features have been related to the cage opening, which is here modeled as a sequence of bond breakings.

Simulated Thermal Effects on Structural and Electronic Properties of GaN

1995 ◽  
Vol 395 ◽  
Author(s):  
S. Serra ◽  
L. Miglio ◽  
Vincenzo Fiorentini
Keyword(s):  
Molecular Dynamics ◽  
Phase Diagram ◽  
Band Structure ◽  
Electronic Properties ◽  
Thermal Effects ◽  
Tight Binding ◽  
Local Ordering ◽  
Structural And Electronic Properties ◽  
Experimental Indication ◽  
Experimental Melting

ABSTRACTWe present preliminary results of tight binding molecular dynamics (TBMD) simulations concerning the thermal effects on the structural and electronic properties of GaN. We derived a semiempirical tight binding (TB) potential which is able to reproduce the band structure and the phase diagram of GaN for zincblende, wurtzite and rock-salt phases. We have found that even at few hundreds K above the experimental melting temperature the local ordering is fairly well conserved, with the fraction of wrong bonds quite low. Defects states appear in the gap at approximately 2.3 eV in agreement to the experimental indication for annealed films.

Structural Trends in Amorphous Carbon

1997 ◽  
Vol 498 ◽  
Author(s):  
C. Z. Wang ◽  
K. M. Ho
Keyword(s):  
Molecular Dynamics ◽  
Amorphous Carbon ◽  
Relative Concentration ◽  
Tight Binding ◽  
Binding Potential ◽  
Low Density ◽  
Liquid Carbon ◽  
Wide Range ◽  
Simulation Results ◽  
Dynamics Simulations

ABSTRACTAmorphous carbon (a-C) structures over a wide range of densities are generated by tight-binding molecular dynamics simulations using the recently developed environment-dependent carbon tight-binding potential. Our simulation results show that the relative concentration of the sp2 and sp3 bondings in the a-C samples changes systematically with the density of the samples. The a-C networks obtained by quenching the low density liquids consist of mostly three-fold coordinated atoms while the diamond-like tetrahedral a-C can be generated by quenching the high density (about 3.0g/cm3) liquid carbon.

Structure, intermolecular interactions, and dynamic properties of NTO crystal with impurity defects: A computational study

CrystEngComm ◽  
2021 ◽  
Author(s):  
Jincheng Ji ◽  
Kun Wang ◽  
Simin Zhu ◽  
Weihua Zhu
Keyword(s):  
Crystal Structure ◽  
Molecular Dynamics ◽  
Electronic Properties ◽  
Intermolecular Interactions ◽  
Density Functional ◽  
Computational Study ◽  
Dynamic Properties ◽  
Tight Binding ◽  
Dynamical Properties ◽  
Impurity Defects

Density functional tight binding (DFTB) method and DFTB-based molecular dynamics (DFTB-MD) were employed to study the crystal structure, electronic properties, intermolecular interactions, and dynamical properties of the impurity-contained β-NTO (3-nitro-1,2,4-triazole-5-one)...

Impact of vibronic coupling effects on light-driven charge transfer in pyrene-functionalized middle and large-sized Metalloid Gold Nanoclusters from Ehrenfest dynamics.

2021 ◽  
Author(s):  
Adrian Dominguez-Castro ◽  
Thomas Frauenheim
Keyword(s):  
Molecular Dynamics ◽  
Charge Transfer ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Gold Nanoclusters ◽  
Tight Binding ◽  
Time Dependent ◽  
Effective Strategy ◽  
Dynamics Simulations ◽  
Dependent Density

Theoretical calculations are an effective strategy to comple- ment and understand experimental results in atomistic detail. Ehrenfest molecular dynamics simulations based on the real-time time-dependent density functional tight-binding (RT-TDDFTB) approach...

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