Molecular-Dynamics Study of the Growth of Si1-xGex on Si(100)2×1

1990 ◽  
Vol 202 ◽  
Author(s):  
Stéphane Ethier ◽  
Laurent J. Lewis
Keyword(s):  
Molecular Dynamics ◽  
High Temperature ◽  
Molecular Beam ◽  
Experimental Studies ◽  
Epitaxial Films ◽  
High Temperature Annealing ◽  
Effective Potentials ◽  
Molecular Beam Epitaxial ◽  
Dynamics Simulations ◽  
Substrate Temperatures

ABSTRACTWe use molecular-dynamics simulations to study the growth of pure Si, Si0.5Ge0.5 and pure Ge on the reconstructed (100) surface of Si. The atoms interact with one another via effective potentials of the Stillinger-Weber form with parameters adjusted such as to describe all types of triplet interactions. Motivated by recent experimental studies of molecular-beam epitaxial films,1 we examine in particular the structure of the deposits for various substrate temperatures. We also examine the relaxation of the structure resulting from high-temperature annealing. Finally, we investigate the interdiffusion of the species at the substrate-deposit interface.

Epitaxial growth of Si1−xGex on Si(100)2 × 1: A molecular-dynamics study

1992 ◽  
Vol 7 (10) ◽  
pp. 2817-2827 ◽  
Author(s):  
Stéphane Ethier ◽  
Laurent J. Lewis
Keyword(s):  
Molecular Dynamics ◽  
Epitaxial Growth ◽  
Experimental Studies ◽  
Theoretical Work ◽  
Effective Potentials ◽  
High Substrate ◽  
Reconstructed Surface ◽  
Dynamics Simulations ◽  
Substrate Temperatures

We use molecular-dynamics simulations to study the growth of pure Si, Si0.5Ge0.5, and pure Ge on the 2 × 1 reconstructed surface of Si(100) in a way appropriate to the fabrication of thin films by the method of molecular-beam epitaxy (MBE), namely sequential deposition of energetic atoms. The atoms interact with one another via effective potentials of the Stillinger–Weber form, with parameters adjusted such as to describe all possible types of triplet interactions. Motivated by numerous experimental studies of MBE-grown films, we investigate in particular the structure of the deposits as a function of substrate temperature. We find in all three cases that at low substrate temperatures, poorly ordered structures form, while at high substrate temperatures, epitaxial growth takes place. The presence of Ge limits the number of crystalline overlayers that form, even though it appears to favor a more-ordered structure in the initial stages of growth. For pure Ge epitaxy, in particular, only the first three layers are crystalline, after which growth appears to proceed by the formation of islands, reminiscent of the Stranski–Krastanow growth scheme, and in qualitative agreement with recent experimental and theoretical work. In all samples, annealing improves the quality of the films—at least when grown at sufficiently high substrate temperatures. The interdiffusion of the species at the substrate-deposit interface is also examined.

Mechanisms of Molecular Beam Epitaxial Growth on Reconstructed Si{100}: Thermal and Energized Beams

1988 ◽  
Vol 141 ◽  
Author(s):  
B. J. Garrison ◽  
M. T. Miller ◽  
D.W. Brenner
Keyword(s):  
Molecular Dynamics ◽  
Low Temperature ◽  
Epitaxial Growth ◽  
Gas Phase ◽  
Molecular Beam ◽  
Energy Deposition ◽  
Amorphous Structure ◽  
Molecular Beam Epitaxial ◽  
Dynamics Simulations ◽  
Molecular Beam Epitaxial Growth

Summary:Molecular dynamics simulations have been performed that examine the microscopic mechanisms of rearrangements of atoms on the Si{ 1001 surface due to deposition of gas phase atoms. For thermal energy deposition we find that the gas atoms initially attach to dangling bonds of the surface dimer atoms. The dimer ’unreconstruction’ is due to a diffusion event on the surface, thus is temperature activated. We also find that dimers may open in regions of the surface where there are several atoms not at lattice sites, thus a low temperature amorphous structure. For 5-10 eV deposition there are direct mechanisms of dimer opening that occur on the 50-100 fs timescale. For energies greater than 15-20 eV there is implantation of the silicon atoms which leads to subsurface damage.

scholarly journals Reactive molecular dynamics simulation of the high-temperature pyrolysis of 2,2′,2′′,4,4′,4′′,6,6′,6′′-nonanitro-1,1′:3′,1′′-terphenyl (NONA)

RSC Advances ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 5507-5515
Author(s):  
Liang Song ◽  
Feng-Qi Zhao ◽  
Si-Yu Xu ◽  
Xue-Hai Ju
Keyword(s):  
Molecular Dynamics ◽  
High Temperature ◽  
Molecular Dynamics Simulation ◽  
Molecular Dynamics Simulations ◽  
Dynamics Simulation ◽  
Reactive Molecular Dynamics ◽  
Ring Compounds ◽  
Fused Ring ◽  
Dynamics Simulations

The bimolecular and fused ring compounds are found in the high-temperature pyrolysis of NONA using ReaxFF molecular dynamics simulations.

scholarly journals Molecular dynamics simulations and experimental studies reveal differential permeability of withaferin-A and withanone across the model cell membrane

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Renu Wadhwa ◽  
Neetu Singh Yadav ◽  
Shashank P. Katiyar ◽  
Tomoko Yaguchi ◽  
Chohee Lee ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Cell Membrane ◽  
Molecular Dynamics Simulations ◽  
Experimental Studies ◽  
Bilayer Membrane ◽  
Withaferin A ◽  
Head Group ◽  
Polar Head Group ◽  
Natural Drugs ◽  
Dynamics Simulations

AbstractPoor bioavailability due to the inability to cross the cell membrane is one of the major reasons for the failure of a drug in clinical trials. We have used molecular dynamics simulations to predict the membrane permeability of natural drugs—withanolides (withaferin-A and withanone) that have similar structures but remarkably differ in their cytotoxicity. We found that whereas withaferin-A, could proficiently transverse through the model membrane, withanone showed weak permeability. The free energy profiles for the interaction of withanolides with the model bilayer membrane revealed that whereas the polar head group of the membrane caused high resistance for the passage of withanone, the interior of the membrane behaves similarly for both withanolides. The solvation analysis further revealed that the high solvation of terminal O5 oxygen of withaferin-A was the major driving force for its high permeability; it interacted with the phosphate group of the membrane that led to its smooth passage across the bilayer. The computational predictions were tested by raising and recruiting unique antibodies that react to withaferin-A and withanone. The time-lapsed analyses of control and treated cells demonstrated higher permeation of withaferin-A as compared to withanone. The concurrence between the computation and experimental results thus re-emphasised the use of computational methods for predicting permeability and hence bioavailability of natural drug compounds in the drug development process.

scholarly journals Study of High-Temperature Behaviour of ZnO by Ab Initio Molecular Dynamics Simulations and X-ray Absorption Spectroscopy

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5206
Author(s):  
Dmitry Bocharov ◽  
Inga Pudza ◽  
Konstantin Klementiev ◽  
Matthias Krack ◽  
Alexei Kuzmin
Keyword(s):  
Molecular Dynamics ◽  
High Temperature ◽  
Ab Initio ◽  
Ab Initio Molecular Dynamics ◽  
Mean Square ◽  
Structural Anisotropy ◽  
X Ray ◽  
Temperature Dependences ◽  
Dynamics Simulations ◽  
X Ray Absorption

Wurtzite-type zinc oxide (w-ZnO) is a widely used material with a pronounced structural anisotropy along the c axis, which affects its lattice dynamics and represents a difficulty for its accurate description using classical models of interatomic interactions. In this study, ab initio molecular dynamics (AIMD) was employed to simulate a bulk w-ZnO phase in the NpT ensemble in the high-temperature range from 300 K to 1200 K. The results of the simulations were validated by comparison with the experimental Zn K-edge extended X-ray absorption fine structure (EXAFS) spectra and known diffraction data. AIMD NpT simulations reproduced well the thermal expansion of the lattice, and the pronounced anharmonicity of Zn–O bonding was observed above 600 K. The values of mean-square relative displacements and mean-square displacements for Zn–O and Zn–Zn atom pairs were obtained as a function of interatomic distance and temperature. They were used to calculate the characteristic Einstein temperatures. The temperature dependences of the O–Zn–O and Zn–O–Zn bond angle distributions were also determined.

scholarly journals Nanoformulation-by-design: an experimental and molecular dynamics study for polymer coated drug nanoparticles

RSC Advances ◽  
2020 ◽  
Vol 10 (33) ◽  
pp. 19521-19533 ◽  
Author(s):  
Ioanna Danai Styliari ◽  
Vincenzo Taresco ◽  
Andrew Theophilus ◽  
Cameron Alexander ◽  
Martin Garnett ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Experimental Studies ◽  
High Drug ◽  
Nanoparticle Formation ◽  
Polymer Nanoparticle ◽  
Drug Nanoparticles ◽  
Dynamics Simulations

Experimental studies of drug–polymer nanoparticle formation combined with molecular dynamics simulations provide atomistic explanations for the high drug loadings obtained.

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