Local Structural Changes Around Charged Dangling Bonds

1996 ◽  
Vol 420 ◽  
Author(s):  
R. Biswas ◽  
Qiming Li
Keyword(s):  
Energy Minimization ◽  
Local Structure ◽  
Structural Changes ◽  
Nearest Neighbor ◽  
Energy Surface ◽  
Optical Transition ◽  
Tight Binding ◽  
Dangling Bond ◽  
Fast Relaxation ◽  
Minimization Procedure

AbstractTight-binding total energy calculations are used to describe the changes in local structure following either electron or hole capture by a neutral dangling bond in computer generated a-Si:H models. After the change in charge state, the structure is allowed to relax by a steepest descent energy minimization procedure. Generally the local bond angles increase (decrease) rapidly by 3- 100 in transitions from the D0 to the D+ (D-) configurations. The displacement of nearest neighbor atoms and nearby H atoms is large (more than 0.2 Å), but displacement of distant atoms is generally much smaller. Calculated optical transition levels have the D- level below D0 and the D+ level above D0. The fast relaxation of the charged defect configurations suggest a smooth energy surface for the relaxation.

Energies and Electric Dipole Moments of the Bound Vibrational States of HN2+ and DN2+

2008 ◽  
Vol 73 (6-7) ◽  
pp. 873-897 ◽  
Author(s):  
Vladimír Špirko ◽  
Ota Bludský ◽  
Wolfgang P. Kraemer
Keyword(s):  
Dipole Moment ◽  
Nearest Neighbor ◽  
Energy Surface ◽  
Dipole Moments ◽  
Three Dimensional ◽  
Vibrational States ◽  
Spacing Distribution ◽  
Triatomic Molecules ◽  
Vibrational Levels ◽  
Different Levels

The adiabatic three-dimensional potential energy surface and the corresponding dipole moment surface describing the ground electronic state of HN2+ (Χ1Σ+) are calculated at different levels of ab initio theory. The calculations cover the entire bound part of the potential up to its lowest dissociation channel including the isomerization barrier. Energies of all bound vibrational and low-lying ro-vibrational levels are determined in a fully variational procedure using the Suttcliffe-Tennyson Hamiltonian for triatomic molecules. They are in close agreement with the available experimental numbers. From the dipole moment function effective dipoles and transition moments are obtained for all the calculated vibrational and ro-vibrational states. Statistical tools such as the density of states or the nearest-neighbor level spacing distribution (NNSD) are applied to describe and analyse general patterns and characteristics of the energy and dipole results calculated for the massively large number of states of the strongly bound HN2+ ion and its deuterated isotopomer.

Electrical Transport Properties of Carbon Nanotube Metal-Semiconductor Heterojunction

2016 ◽  
Vol 15 (05n06) ◽  
pp. 1660009 ◽  
Author(s):  
Keka Talukdar ◽  
Anil Shantappa
Keyword(s):  
Electrical Transport ◽  
Nearest Neighbor ◽  
Electronic Devices ◽  
Tight Binding ◽  
Transmission Function ◽  
Topological Defects ◽  
Dynamics Simulation ◽  
Internal Stresses ◽  
Electrical Transport Properties ◽  
Tight Binding Approximation

Carbon nanotubes (CNTs) have been proved to have promising applicability in various fields of science and technology. Their fascinating mechanical, electrical, thermal, optical properties have caught the attention of today’s world. We have discussed here the great possibility of using CNTs in electronic devices. CNTs can be both metallic and semiconducting depending on their chirality. When two CNTs of different chirality are joined together via topological defects, they may acquire rectifying diode property. We have joined two tubes of different chiralities through circumferential Stone–Wales defects and calculated their density of states by nearest neighbor tight binding approximation. Transmission function is also calculated to analyze whether the junctions can be used as electronic devices. Different heterojunctions are modeled and analyzed in this study. Internal stresses in the heterojunctions are also calculated by molecular dynamics simulation.

Ascertaining the nanocluster formation within an ion-irradiated Pt/Ni/C multi-trilayer with X-ray absorption spectroscopy

2012 ◽  
Vol 20 (1) ◽  
pp. 137-144
Author(s):  
Nitya Ramanan ◽  
Sumalay Roy ◽  
Debdutta Lahiri ◽  
Surinder M. Sharma ◽  
B. N. Dev
Keyword(s):  
Absorption Spectroscopy ◽  
Structural Changes ◽  
Nearest Neighbor ◽  
Ion Irradiation ◽  
Physical Adsorption ◽  
X Ray ◽  
Bimetallic Nanoclusters ◽  
Wave Technique ◽  
Wide Scale ◽  
X Ray Absorption

In this work nanoclusters formed in a Pt/Ni/C multi-trilayer by the ion-irradiated method of synthesis are characterized. In particular, an attempt to understand the role of interfaces in the synthesis is made. With this objective, ion-irradiation-induced structural changes in a Pt/Ni/C multi-trilayer using X-ray absorption spectroscopy (at the NiK-edge) in conjunction with the X-ray standing-wave technique are investigated. The XANES analysis identifies chemical binding at pristine Ni/C and Ni/Pt interfaces, in contrast with physical adsorption at the Pt/C interface. The chemical nature of the interfaces determines their relative stability with respect to irradiation and controls the extent of metallic diffusion. The most interesting structural change, upon irradiation, is the disruption of the Pt/C interface and subsequent migration of Pt atoms towards pre-diffused Ni atoms within the C layer, leading to the formation of Ni-centered Ni–Pt bimetallic nanoclusters (with Ni:Pt = 60:40). These clusters are highly disordered beyond their nearest neighbor and find wide-scale applications as, for example, magnetic devicesetc. The implications of these findings on the design goals are discussed.

scholarly journals Accurate six-band nearest-neighbor tight-binding model for the π-bands of bulk graphene and graphene nanoribbons

2011 ◽  
Vol 109 (10) ◽  
pp. 104304 ◽  
Author(s):  
Timothy B. Boykin ◽  
Mathieu Luisier ◽  
Gerhard Klimeck ◽  
Xueping Jiang ◽  
Neerav Kharche ◽  
...  
Keyword(s):  
Nearest Neighbor ◽  
Graphene Nanoribbons ◽  
Tight Binding ◽  
Tight Binding Model ◽  
Binding Model

scholarly journals ON THE VERDET CONSTANT AND FARADAY ROTATION FOR GRAPHENE-LIKE MATERIALS

2013 ◽  
Vol 25 (04) ◽  
pp. 1350007 ◽  
Author(s):  
MIKKEL H. BRYNILDSEN ◽  
HORIA D. CORNEAN
Keyword(s):  
Taylor Expansion ◽  
Nearest Neighbor ◽  
Tight Binding ◽  
Transverse Component ◽  
Tight Binding Model ◽  
Binding Model ◽  
Gauge Invariant ◽  
Verdet Constant ◽  
Absolute Value ◽  
Computable Formula

We present a rigorous and rather self-contained analysis of the Verdet constant in graphene-like materials. We apply the gauge-invariant magnetic perturbation theory to a nearest-neighbor tight-binding model and obtain a relatively simple and exactly computable formula for the Verdet constant, at all temperatures and all frequencies of sufficiently large absolute value. Moreover, for the standard nearest-neighbor tight-binding model of graphene we show that the transverse component of the conductivity tensor has an asymptotic Taylor expansion in the external magnetic field where all the coefficients of even powers are zero.

Transfer Integrals and Band Structures in (Et)2X Salts

1989 ◽  
Vol 173 ◽  
Author(s):  
Oliver H. Leblanc ◽  
Margaret L. Blohm ◽  
Richard P. Messmer
Keyword(s):  
Low Temperature ◽  
Nearest Neighbor ◽  
Spherical Wave ◽  
Tight Binding ◽  
Ab Initio Method ◽  
Energy Bands ◽  
Hubbard Hamiltonian ◽  
Transfer Integrals ◽  
Semi Empirical ◽  
Very Low Temperature

ABSTRACTTransfer integrals (tij) between pairs of nearest neighbor ET molecules were calculated by an ab initio method. Tight-binding one-electron energy bands constructed from the tij are similar to those previously calculated by Mori and by Whangbo and their coworkers by semi-empirical, extended Hückel methods, but quite different from those found by Kübler et al. in β-(ET)2I3 using the augmented spherical wave (ASW) method. However, all these band models are suspect. The Hubbard on-site repulsion parameter U is estimated to be about twice the band widths, indicating that a full treatment of the Hubbard hamiltonian is needed. Also, polaron effects appear to control transport except at very low temperature.

Infrared Electroabsorption Spectra in Amorphous Silicon Solar Cells

1999 ◽  
Vol 557 ◽  
Author(s):  
J. H. Lyou ◽  
Eric A. Schiff ◽  
Steven S. Hegedus ◽  
S. Guha ◽  
J. Yang
Keyword(s):  
Solar Cells ◽  
Infrared Spectrum ◽  
Amorphous Silicon ◽  
Optical Transition ◽  
Silicon Solar Cells ◽  
Reverse Bias Voltage ◽  
Dangling Bond ◽  
Applied Bias ◽  
Infrared Band ◽  
Peak Energy

AbstractWe report measurements of the infrared spectrum detected by modulating the reverse-bias voltage across amorphous silicon pin solar cells and Schottky barrier diodes. We find a band with a peak energy of 0.8 eV. The existence of this band has not, to our knowledge, been reported previously. The strength of the infrared band depends linearly upon applied bias, as opposed to the quadratic dependence for interband electroabsorption in amorphous silicon.The band's peak energy agrees fairly well with the known optical transition energies for dangling bond defects, but the linear dependence on bias and the magnitude of the signal are surprising if interpreted using an analogy to interband electroabsorption. A model based on absorption by defects near the n/i interface of the diodes accounts well for the infrared spectrum.

New Tight-Binding Pair Potentials for Mineral Oxides: Application to β-Cassiterite (110), β-Tridymite (10TO) and Cristobalite (110)

1992 ◽  
Vol 278 ◽  
Author(s):  
T. J. Godin ◽  
John P. Lafemina
Keyword(s):  
Total Energy ◽  
Nearest Neighbor ◽  
Tight Binding ◽  
Insulating Materials ◽  
Atomic Structures ◽  
Pair Potentials ◽  
Mineral Oxides ◽  
Distant Neighbor

AbstractTight-binding, total-energy (TBTE) methods have successfully predicted surface atomic geometries for a variety of semiconducting and insulating materials that are well described by a nearest-neighbor model of interatomic interactions. However, little work has been done on distant-neighbor models, which are required to study many important mineral oxides. In this paper we demonstrate one way in which the TBTE methodology can be extended to these materials. To illustrate this approach, we calculate surface atomic structures for cassiterite SnO2 (110), β-cristobalite SiO2 (110) and βtridymite SiO2 (10TO).

Lattice Dynamics and Network Dynamics Calculations on Vibrational Modes of Lithium Borate Glasses

1990 ◽  
Vol 210 ◽  
Author(s):  
J. Deppe ◽  
M. Balkanski ◽  
R. F. Wallis ◽  
M. Massot
Keyword(s):  
Lattice Dynamics ◽  
Structural Changes ◽  
Structural Model ◽  
Nearest Neighbor ◽  
Network Dynamics ◽  
Borate Glasses ◽  
Vibrational Modes ◽  
Good Qualitative Agreement ◽  
Covalently Bonded ◽  
The Family

AbstractThe central force nearest neighbor model for glasses is used to discuss the Raman and infrared vibrational data for the family of lithium doped borate glasses B2O3 - xLi2O. The addition of the dopant is shown to cause local structural changes, including the transformation of three-coordinated borons to four-coordinated ones. An extremely simple structural model for the glass gives good qualitative agreement with experiment. The results of lattice dynamics calculations fall within the allowed frequency band limits predicted by network dynamics. The success of this model illustrates the importance of short range order on the vibrational spectra of covalently bonded solids.

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