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.

Tight Binding Modeling of Properties Related to Field Emission from Nanodiamond Clusters

2000 ◽  
Vol 621 ◽  
Author(s):  
Denis A. Areshkin ◽  
Olga A. Shenderova ◽  
Victor V. Zhirnov ◽  
Alexander F. Pal ◽  
John J. Hren ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Field Emission ◽  
Density Of States ◽  
Electron Affinity ◽  
Potential Distribution ◽  
Tight Binding ◽  
Matrix Elements ◽  
Energy States ◽  
Bulk Diamond ◽  
Modeling Of Properties

ABSTRACTThe electronic structure of nanodiamond clusters containing between 34 and 913 carbon atoms was calculated using a tight-binding Hamiltonian. All clusters had shapes represented by an octahedron with (111) facets with the top and the bottom vertices truncated to introduce (100) surfaces. The tight-binding Hamiltonian consisted of environment-dependent matrix elements, and C-H parameters fit to reproduce energy states of the cyclic C6 and methane. The calculations predict a density of states similar to bulk diamond for clusters with radii greater than ∼2.5nm, and insignificant differences in the potential distribution between the clusters and bulk diamond for radii greater than ∼1nm. Hydrogen passivated nanodiamond clusters are estimated to have an electron affinity of approximately -1.8 eV.

Parameter free calculation of the subgap density of states in poly(3-hexylthiophene)

2014 ◽  
Vol 174 ◽  
pp. 255-266 ◽  
Author(s):  
Jarvist M. Frost ◽  
James Kirkpatrick ◽  
Thomas Kirchartz ◽  
Jenny Nelson
Keyword(s):  
Density Of States ◽  
Energy Levels ◽  
Tight Binding ◽  
Electronic Energy ◽  
Film Structure ◽  
Dynamics Simulation ◽  
Characteristic Energy ◽  
Torsional Potential ◽  
Experimental Values ◽  
Electronic Energy Levels

We investigate the influence of intra-chain and inter-chain interactions on the sub-gap density of states in a conjugated polymer using a combination of atomistic molecular dynamics simulation of polymer film structure and tight-binding calculation of electronic energy levels. For disordered assemblies of poly-3-hexylthiophene we find that the tail of the density of hole states is approximately exponential with a characteristic energy of 37 meV, which is similar to experimental values. This tail of states arises mainly from variations in the electronic coupling between neighbouring monomers, and is only slightly influenced by interchain coupling. Thus, knowledge of the disorder in torsion between neighbouring monomers is sufficient to estimate the density of states for the polymer. However, the intrachain torsional disorder is determined largely by the packing of the chains rather than the torsional potential alone. We propose the combination of methods as a tool to design higher mobility conjugated polymers.

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.

ON THE COUPLING BETWEEN ELECTRONS AND SOFT-MODE PHONONS IN La2CuO4

1990 ◽  
Vol 04 (07) ◽  
pp. 489-496 ◽  
Author(s):  
Z. K. PETRU ◽  
N. M. PLAKIDA
Keyword(s):  
Fermi Energy ◽  
Soft Mode ◽  
Tight Binding ◽  
Electronic Energy ◽  
Tight Binding Model ◽  
Energy Bands ◽  
Phonon Modes ◽  
Binding Model ◽  
Bond Bending ◽  
Electronic Energy Bands

An interaction between soft bond-bending phonon modes and localized 3d – 2p electrons is considered. Its strength is estimated to be of the order of 1 eV/Å. By means of the tight-binding model, the electronic energy bands of La 2 CuO 4 are calculated. It is explicitly shown that a tetragonal to orthorhombic transition does not open a gap at the Fermi energy.

Theoretical Studies of Oxygen Vacancies in YBa2Cu3O7-y

1987 ◽  
Vol 99 ◽  
Author(s):  
Brent A. Richert ◽  
Roland E. Allen
Keyword(s):  
Electronic Structure ◽  
Density Of States ◽  
Fermi Energy ◽  
Oxygen Vacancies ◽  
Tight Binding ◽  
Theoretical Studies ◽  
Metal Atoms

ABSTRACTWe have performed semiempirical tight-binding calculations of the electronic structure of YBa2Cu3O7, with dand s orbitals included for all the metal atoms and p and sorbitals for oxygen. Here we report studies of oxygen vacancies on the O(1) chain sites in YBa2Cu3O7-y. The modification of the density of states ρ(E) and the shift of the Fermi energy Ep were calculated for 0 < y ≤ 1.0. The Fermi energy is found to increase monotonically with y, confirming the expectation that oxygen vacancies act as donors. Also, ρ(EF)is found to decrease with y.

Magnetic Volume Effect of Hydrogen Diffusion in Palladium

2020 ◽  
Vol 310 ◽  
pp. 29-33
Author(s):  
Sarantuya Nasantogtokh ◽  
Xin Cui ◽  
Zhi Ping Wang
Keyword(s):  
Transition Metal ◽  
Density Of States ◽  
Density Functional ◽  
Hydrogen Diffusion ◽  
Magnetic Moments ◽  
Interstitial Site ◽  
Volume Effect ◽  
Face Centered Cubic ◽  
Hydrogen Atoms ◽  
Octahedral Interstitial Site

The electronic and magnetic properties of palladium hydrogen are investigated using first-principles spin-polarized density functional theory. By studying the magnetic moments and electronic structures of hydrogen atoms diffusing in face-centered cubic structure of transition metal Pd, we found that the results of magnetic moments are exactly the same in the two direct octahedral interstitial site-octahedral interstitial site diffusion paths-i.e. the magnetic moments are the largest in the octahedral interstitial site, and the magnetic moments are the lowest in saddle point positions. We also studied on the density of states of some special points, with the result that the density of states near the Fermi level is mainly contributed by 4d electrons of Pd and the change of magnetic moments with the cell volume in the unit cell of transition metal Pd with a hydrogen atom.

Trace-map invariant and zero-energy states of the tight-binding Rudin-Shapiro model

1992 ◽  
Vol 46 (6) ◽  
pp. 3296-3304 ◽  
Author(s):  
Mihnea Dulea ◽  
Magnus Johansson ◽  
Rolf Riklund
Keyword(s):  
Tight Binding ◽  
Zero Energy ◽  
Trace Map ◽  
Energy States

ENERGY GAP DEPENDENCE ON ANION CONCENTRATION FOR GaxIn1-xAsyP1-y QUATERNARY ALLOY BY RECURSION METHOD

2004 ◽  
Vol 18 (18) ◽  
pp. 955-962
Author(s):  
MUSA EL-HASAN ◽  
REZEK ESTATIEH
Keyword(s):  
Density Of States ◽  
Energy Gap ◽  
Local Density ◽  
Tight Binding ◽  
Quaternary Alloy ◽  
Average Density ◽  
Local Density Of States ◽  
Recursion Method ◽  
Orbital Decomposition ◽  
Lattice Matched

Three terminators have been tested, square root terminator, quadreture terminator and linear terminator, it was found that the linear terminator is the best, so it was used in calculating local density of states (LDOS) and it's orbital decomposition, alloy average density of states, and energy gap for different anion concentrations for InP lattice matched alloy. The results were compared with our previous calculations of (LDOS), and results from other methods. Energy gap was compared with experimental measurements. A five orbital sp3s* per atom model was used in the tight-binding representation of the Hamiltonian.

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