Computational Study of Interstitial Hydrogen Atoms in Nano-Diamond Grains Embedded in an Amorphous Carbon Shell

2011 ◽  
Vol 9 (4) ◽  
pp. 843-858 ◽  
Author(s):  
Amihai Silverman ◽  
Alon Hoffman ◽  
Joan Adler
Keyword(s):  
Amorphous Carbon ◽  
Formation Energy ◽  
Computational Study ◽  
Tight Binding ◽  
Carbon Matrix ◽  
Amorphous Region ◽  
Energy Difference ◽  
Carbon Shell ◽  
Hydrogen Atoms ◽  
Diamond Grain

AbstractThe properties of hydrogen atoms in a nano-diamond grain surrounded by an amorphous carbon shell are studied with Tight Binding computer simulations. Our samples model nano-diamond grains, of a few nanometers in size, that nucleate within an amorphous carbon matrix, as observed in deposition from a hydrocarbon rich plasma. The calculations show that the average hydrogen interstitial formation energy in the amorphous region is lower than in the nano-diamond core, therefore hydrogen interstitial sites in the in the amorphous region are more stable than in the nano-diamond core. This formation energy difference is the driving force for the diffusion of hydrogen atoms from nano-diamond grains into amorphous carbon regions. An energy well was observed on the amorphous side of the nano-diamond amorphous carbon interface: hydrogen atoms are expected to be trapped here. This scenario agrees with experimental results which show that hydrogen retention of diamond films increases with decreasing grain size, and suggest that hydrogen is bonded and trapped in nano-diamond grain boundaries and on internal grain surfaces.

HYDROGEN BONDING IN DIAMOND: A COMPUTATIONAL STUDY

2006 ◽  
Vol 17 (07) ◽  
pp. 959-966 ◽  
Author(s):  
O. OFER ◽  
JOAN ADLER ◽  
A. HOFFMAN
Keyword(s):  
Density Of States ◽  
Fermi Energy ◽  
Computational Study ◽  
Tight Binding ◽  
Local Deformation ◽  
Electronic Energy ◽  
Hydrogen Atoms ◽  
High Hydrogen ◽  
New Energy ◽  
Energy States

We present tight binding molecular dynamics simulations of the diffusion and bonding of hydrogen in bulk diamond. The motion of hydrogen atoms and the resultant structural and electronic energy level changes are investigated. The hydrogen atoms were found to have a tendency to migrate to the surface layer of diamond, resulting in a local deformation of the lattice, creating new energy states above and below the Fermi energy in the bandgap of the diamond density of states. In the diamond bulk, at high hydrogen concentrations, vacancies created by a hydrogen atom are quickly filled with other hydrogen atoms causing a deformation of the diamond lattice, inducing H 2 formation. This creates new energy states above the Fermi energy and reduces the secondary bandgap of the diamond density of states.

Formation of Nanostructured Coating Based on the Amorphous Carbon Matrix and Silver Nanocrystallites

2016 ◽  
Vol 8 (4(1)) ◽  
pp. 04019-1-04019-6 ◽  
Author(s):  
A. Ya. Kolpakov ◽  
◽  
A. I. Poplavsky ◽  
S. S. Manokhin ◽  
M. E. Galkina ◽  
...  
Keyword(s):  
Amorphous Carbon ◽  
Carbon Matrix ◽  
Nanostructured Coating

scholarly journals Investigation of the Antibacterial Properties of Silver-Doped Amorphous Carbon Coatings Produced by Low Pressure Magnetron Assisted Acetylene Discharges

2022 ◽  
Vol 23 (1) ◽  
pp. 563
Author(s):  
Valentin Job ◽  
Julie Laloy ◽  
Vincent Maloteau ◽  
Emile Haye ◽  
Stéphane Lucas ◽  
...  
Keyword(s):  
Antibacterial Activity ◽  
Amorphous Carbon ◽  
Antibacterial Properties ◽  
Carbon Matrix ◽  
Modes Of Transmission ◽  
Gram Positive Bacteria ◽  
Multiple Exposures ◽  
Environmental Surfaces ◽  
Hospital Acquired ◽  
Amorphous Carbon Coatings

Hospital-acquired infections are responsible for a significant part of morbidity and mortality. Among the possible modes of transmission, this study focuses on environmental surfaces by developing innovative antibacterial coatings that can be applied on interior fittings in hospitals. This work aims to optimize a coating made of an amorphous carbon matrix doped with silver (a-C:H:Ag) produced by a hybrid PVD/PECVD process and to evaluate its antibacterial activity. We present a coating characterization (chemical composition and morphology) as well as its stability in an ageing process and after multiple exposures to bacteria. The antibacterial activity of the coatings is demonstrated against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) bacteria through several bioassays. Moreover, the data suggest a crucial role of silver diffusion towards the surface and nanoparticle formation to explain the very promising anti-bacterial activities reported in this work.

Tight-Binding Molecular Dynamics Study of Liquid and Amorphous Carbon

1992 ◽  
Vol 291 ◽  
Author(s):  
C. Z. Wang ◽  
K. M. Ho ◽  
C. T. Chan
Keyword(s):  
Experimental Data ◽  
Molecular Dynamics ◽  
Ab Initio ◽  
Molecular Dynamics Simulations ◽  
Amorphous Carbon ◽  
Simulation Study ◽  
Tight Binding ◽  
Sufficient Accuracy ◽  
Complex Carbon ◽  
Dynamics Simulations

ABSTRACTTight-binding molecular-dynamics simulations are performed to study the structure of liquid and amorphous carbon. Comparisons of our results with ab initiomolecular dynamics (Car-Parrinello) results and experimental data show that the scheme has sufficient accuracy and efficiency for realistic simulation study of the structural properties of complex carbon systems.

scholarly journals Microwave Absorption of Crystalline Fe/MnO@C Nanocapsules Embedded in Amorphous Carbon

2020 ◽  
Vol 12 (1) ◽  
Author(s):  
Gaihua He ◽  
Yuping Duan ◽  
Huifang Pang
Keyword(s):  
Dielectric Loss ◽  
Amorphous Carbon ◽  
High Performance ◽  
Magnetic Loss ◽  
Synthesis Method ◽  
Domain Size ◽  
Carbon Matrix ◽  
Effective Bandwidth ◽  
General Duty ◽  
Enhanced Absorption

AbstractCrystalline Fe/MnO@C core–shell nanocapsules inlaid in porous amorphous carbon matrix (FMCA) was synthesized successfully with a novel confinement strategy. The heterogeneous Fe/MnO nanocrystals are with approximate single-domain size which gives rise to natural resonance in 2–18 GHz. The addition of MnO2 confines degree of graphitization catalyzed by iron and contributes to the formation of amorphous carbon. The heterogeneous materials composed of crystalline–amorphous structures disperse evenly and its density is significantly reduced on account of porous properties. Meanwhile, adjustable dielectric loss is achieved by interrupting Fe core aggregation and stacking graphene conductive network. The dielectric loss synergistically with magnetic loss endows the FMCA enhanced absorption. The optimal reflection loss (RL) is up to − 45 dB, and the effective bandwidth (RL < − 10 dB) is 5.0 GHz with 2.0 mm thickness. The proposed confinement strategy not only lays the foundation for designing high-performance microwave absorber, but also offers a general duty synthesis method for heterogeneous crystalline–amorphous composites with tunable composition in other fields.

Simulation of Vacancy Pairs in GaN Using Tight-Binding Molecular Dynamics

1997 ◽  
Vol 482 ◽  
Author(s):  
Derrick E. Boucher ◽  
Zoltán A. Gál ◽  
Gary G. DeLeo ◽  
W. Beall Fowler
Keyword(s):  
Molecular Dynamics ◽  
Electronic Structure ◽  
Total Energy ◽  
Formation Energy ◽  
Tight Binding ◽  
Md Simulations ◽  
Shallow Donor ◽  
Shallow Acceptor ◽  
Structure Geometry ◽  
Donor Character

AbstractThe electronic structure, geometry and energetics of Ga vacancy pairs and N vacancy pairs in both wurtzite and zincblende GaN are investigated via molecular dynamics (MD) simulations using an empirical tight-binding (TB) model with total energy capabilities and supercells containing up to 216 atoms. Our calculations suggest that, by pairing, N vacancies, which in isolation act as shallow donors, can lower their collective formation energy by about 5 eV. In doing so, however, these N vacancies lose their shallow-donor character as the lattice relaxes in response to this aggregation. Contrasting with the N vacancies, the Ga vacancies are found to retain their isolated shallow acceptor behavior and do not gain significant energy upon aggregation. The possible implications for larger aggregate defects are discussed.

scholarly journals A simple model for growth of a planar hydrogenated carbon cluster under interstellar or circumstellar conditions

1997 ◽  
Vol 180 ◽  
pp. 268-268
Author(s):  
G. Pascoli
Keyword(s):  
Numerical Simulation ◽  
Simple Model ◽  
Amorphous Carbon ◽  
Carbon Cluster ◽  
Carbon Clusters ◽  
Hydrogen Atoms ◽  
Simulation Code ◽  
Carbon Chains ◽  
Physico Chemical ◽  
Open Question

The physico-chemical origin of the hydrogenated carbon clusters (cumulenes, PAHs, graphite or amorphous carbon) in space is still an open question. We have worked out a numerical simulation code in order to build up planar (graphite-like) carbon clusters. We assume that hydrogen atoms can fix on the carbon skeleton following a random process allowing for H2 formation. The structures we have found are very complex. In a given cluster, several molecular entities can simultaneously be present: (sp2) carbon chains, rings or compact formations (aromatic structures or small PAHs). We argue that these very contorted hydrogenated structures could be ubiquitous in the interstellar medium, in carbon-rich circumstellar regions and in PNe.

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