scholarly journals Density-functional Based Tight-binding Calculations on Thiophene Polymorphism

VLSI Design ◽  
2001 ◽  
Vol 13 (1-4) ◽  
pp. 393-397
Author(s):  
J. Widany ◽  
G. Daminelli ◽  
A. Di Carlo ◽  
P. Lugli
Keyword(s):  
Total Energy ◽  
Intermolecular Interaction ◽  
Density Functional ◽  
Tight Binding ◽  
Methyl Groups ◽  
Direct Function ◽  
Energy Calculations ◽  
Polymorphic Modifications

Total energy calculations based on a density-functional tight-binding scheme have been performed on polymorphic modifications of various thiophene crystals. The investigated structures include sulphanyl-substituted quater-thiophene and methyl-substituted sexithiophene, in the monoclinic and triclinic modifications. Attention has been focused on the intermolecular interaction between the molecular units. Despite the similarities in the backbone geometries, the strength and nature of intermolecular interaction differs largely in the various polymorphs. Sulphur atoms belonging to the thiophene rings are strongly involved in the interaction. Sulphanyl substituents play an important role, while methyl groups do not contribute. The strength of intermolecular interaction is not a direct function of atom distance.

Model potential based on tight-binding total-energy calculations for transition-metal systems

1995 ◽  
Vol 52 (15) ◽  
pp. 11509-11516 ◽  
Author(s):  
Javier Guevara ◽  
Ana Maria Llois ◽  
Mariana Weissmann
Keyword(s):  
Transition Metal ◽  
Total Energy ◽  
Tight Binding ◽  
Model Potential ◽  
Energy Calculations

Structure, Bonding and Stability of Transition Metal Silicides: A Real-Space Perspective by Tight Binding Potentials

1997 ◽  
Vol 491 ◽  
Author(s):  
Leo Miglio ◽  
Francesca Tavazza ◽  
Antonio Garbelli ◽  
Massimo Celino
Keyword(s):  
Molecular Dynamics ◽  
Transition Metal ◽  
Total Energy ◽  
Molecular Dynamics Simulations ◽  
Predictive Power ◽  
Tight Binding ◽  
Real Space ◽  
Energy Calculations ◽  
Metal Silicides ◽  
Dynamics Simulations

ABSTRACTWe point out that the predictive power of tight binding potentials is not limited to obtaining fairly accurate total energy calculations and very satisfactory structural evolutions by molecular dynamics simulations. They also allow for a nice physical picture of the links between bonding and stability in different structures, which is particularly helpful in the case of binary suicides

Experimental and Theoretical Joint Study on the Electronic and Structural Properties of Silicon Nanocrystals Embedded in SiO2: active Role of the Interface Region

2003 ◽  
Vol 770 ◽  
Author(s):  
N. Daldosso ◽  
M. Luppi ◽  
G. Dalba ◽  
L. Pavesi ◽  
F. Rocca ◽  
...  
Keyword(s):  
Total Energy ◽  
Silicon Nanocrystals ◽  
Density Functional ◽  
Light Emission ◽  
Local Environment ◽  
Active Role ◽  
Localized States ◽  
Total Electron ◽  
Energy Calculations ◽  
Si Content

AbstractThe local environment of light emitting silicon nanocrystals (Si-nc) embedded in amorphous SiO2 has been studied by x-ray absorption spectroscopy (XAS) and by ab-initio total energy calculations. Si-nc have been formed by PECVD deposition of SiOx with different Si content (from 35 to 42 at.%) and thermal annealing at high temperature (1250 °C). The comparison between total electron yield (TEY) and photoluminescence yield (PLY) spectra has allowed the identification of a modified region of SiO2 (about 1 nm thick) surrounding the Si-nc, which participates to the light emission of Si-nc. Total energy calculations, within the density functional theory, clearly show that Si-nc are surrounded by a cap-shell of stressed SiO2 with a thickness of about 1 nm. The optoelectronic properties show the appearance of localized states not only in the Si-nc core region but also in the modified SiO2 region.

DISSOCIATION OF PH3 AND AsH3 ON Ge(100)(2x1) SURFACE

2007 ◽  
Vol 14 (03) ◽  
pp. 507-515 ◽  
Author(s):  
ŞENAY KATIRCIOĞLU
Keyword(s):  
Density Functional Theory ◽  
Total Energy ◽  
Density Functional ◽  
Functional Theory ◽  
Energy Calculations ◽  
Dissociation Path ◽  
Stable Structures ◽  
Relative Total Energy

The most stable structures for the dissociation of phosphine and arsine on Ge (100)(2x1) surface have been investigated by relative total energy calculations based on Density Functional Theory. It has been found that the thermodynamically preferred structures in the dissociation path of phosphine and arsine are the same; PH 2 and AsH 2 products prefer to be on a single Ge dimer bond, but PH and AsH prefer to be between the adjacent Ge dimers. According to the optimization calculations, the dissociation path started with the adsorption of PH 3( AsH 3) on the electron deficient side of the Ge dimer bond is ended with the formation of P – P ( As – As ) dimers parallel to the dimers of Ge .

THE BAND-GAP AND TRUE BAND-GAP IN NOMINALLY METALLIC CARBON NANOTUBES: THE TIGHT-BINDING STUDY ON CORRUGATION EFFECT

2014 ◽  
Vol 28 (08) ◽  
pp. 1450018
Author(s):  
HONGXIA LU ◽  
JIANBAO WU ◽  
JIZHEN WANG ◽  
SHAOCONG SHI ◽  
WEIYI ZHANG
Keyword(s):  
Carbon Nanotubes ◽  
Total Energy ◽  
Band Gap ◽  
Tight Binding ◽  
Small Radius ◽  
Single Wall Carbon Nanotubes ◽  
Curvature Effect ◽  
Tight Binding Approximation ◽  
Energy Calculations ◽  
Small Band

In this paper, the band-gap and true band-gap are analyzed for the corrugated structures of various types of single wall carbon nanotubes (SWCNTs) within the tight binding approximation. We show that corrugation, combined with curvature effect, yields naturally the true small band-gap in all SWCNTs with small radius. The more stable corrugated structures of SWCNTs are backed by the abinitio total energy calculations for nominally metallic armchair SWCNTs.

New Insight in Scandium-Mediated Growth Techniques: Sc-Related Defects in 4H-SiC and 6H-SiC

2007 ◽  
Vol 556-557 ◽  
pp. 469-472 ◽  
Author(s):  
Uwe Gerstmann ◽  
Siegmund Greulich-Weber ◽  
E. Rauls ◽  
Johann Martin Spaeth ◽  
Ekaterina N. Kalabukhova ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Total Energy ◽  
Density Functional ◽  
Epr Spectra ◽  
Functional Theory ◽  
Energy Calculations ◽  
Large Anisotropy

Scandium can be used to influence the stoichiometry of SiC during growth of the hexagonal polytypes. Using PL-EPR and total energy calculations in the framework of density functional theory, scandium is predicted to be built in predominantly at the Si-sublattice in form of ScSi acceptors with acceptor levels at 0.55 eV (6H-SiC) and 0.48 eV (4H-SiC). In addition, new PL-EPR spectra are found with a large anisotropy in the g-tensor suggesting defect pairs as an origin.

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