Semiempirical Angular-Force Method for BCC Transition Metals

1990 ◽  
Vol 209 ◽  
Author(s):  
A. E. Carlsson
Keyword(s):  
Transition Metals ◽  
Ab Initio ◽  
Tight Binding ◽  
Energy Difference ◽  
Mechanical Analysis ◽  
Binding Model ◽  
Relaxation Energy ◽  
Electronic Density ◽  
Force Method ◽  
Reconstructed Surface

ABSTRACTAn angular-force method for bcc transition-metals is obtained by generating a functional form via a quantum-mechanical analysis, and subsequently fitting the parameters in this form to experimental and ab-initio theoretical inputs. The quantummechanical analysis uses a four-moment treatment of the electronic density of states (DOS) in a d-band tight-binding model. Calibration of the method gives excellent results for the bcc-fcc energy difference and the vacancy-formation energy in W. The method is used to treat relaxation and c(2 × 2) reconstruction on the W (100) surface. The relaxation energy is primarily due to two-body terms, while the reconstruction requires the angular terms. Agreement with ab-initio results is obtained for reasonable values of the parameters in the model. However, the energy difference between the reconstructed surface and the optimally relaxed surface is quite sensitive to the details of the implementation of the method.

scholarly journals PHASE STABILITY AND ELECTRONIC STRUCTURE OF TRANSITION-METAL ALUMINIDES

1993 ◽  
Vol 07 (01n03) ◽  
pp. 293-298 ◽  
Author(s):  
A. E. CARLSSON
Keyword(s):  
Electronic Structure ◽  
Transition Metal ◽  
Ab Initio ◽  
Phase Stability ◽  
Tight Binding ◽  
Magnetic Behavior ◽  
Binding Model ◽  
Electronic Density ◽  
Model Calculations ◽  
Site Model

This paper will describe the interplay between the electronic structure and structural energetics in simple, complex, and quasicrystalline Al-transition metal (T) intermetallics. The first example is the L1 2− DO 22 competition in Al 3 T compounds. Ab-initio electronic total-energy calculations reveal surprisingly large structural-energy differences, and show that the phase stability of both stoichiometric and ternary-substituted compounds correlates closely with a quasigap in the electronic density of states (DOS). Secondly, ab-initio calculations for the structural stability of the icosahedrally based Al 12 W structure reveal similar quasigap effects, and provide a simple physical explanation for the stability of the complex aluminide structures. Finally, parametrized tight-binding model calculations for the Al–Mn quasicrystal reveal a large spread in the local Mn DOS behavior, and support a two-site model for the quasicrystal's magnetic behavior.

A new spd tight-binding model of magnetism in transition metals

2000 ◽  
Vol 17 (2-4) ◽  
pp. 211-216 ◽  
Author(s):  
C Barreteau ◽  
R Guirado-López ◽  
M.C Desjonquères ◽  
D Spanjaard ◽  
A.M Oleś
Keyword(s):  
Transition Metals ◽  
Tight Binding ◽  
Tight Binding Model ◽  
Binding Model

scholarly journals Ab initio four-band Wannier tight-binding model for generic twisted graphene systems

2021 ◽  
Vol 104 (8) ◽  
Author(s):  
Jin Cao ◽  
Maoyuan Wang ◽  
Shi-Feng Qian ◽  
Cheng-Cheng Liu ◽  
Yugui Yao
Keyword(s):  
Ab Initio ◽  
Tight Binding ◽  
Tight Binding Model ◽  
Binding Model ◽  
Twisted Graphene

A Tight-Binding Model for Molecular Dynamics of Carbon-Hydrogen Systems

1994 ◽  
Vol 358 ◽  
Author(s):  
G. Kopidakis ◽  
C.Z. Wang ◽  
C.M. Soukoulis ◽  
K.M. Ho
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Tight Binding ◽  
Carbon Clusters ◽  
Vibrational Properties ◽  
Tight Binding Model ◽  
Binding Model ◽  
Hydrocarbon Molecules ◽  
Hydrogen Systems

ABSTRACTA model for studying carbon-hydrogen systems with molecular dynamics (MD) is developed based on an empirical tight-binding approach for the calculation of the interatomic forces. The parameters involved are obtained by fitting to the structure of methane. The transferability of the model is tested by reproducing accurately several electronic, structural, and vibrational properties of hydrocarbon molecules. Ab initio results on carbon clusters with hydrogen are compared with the results obtained with our model.

scholarly journals SURFACE EFFECTS ON THE STATISTICS OF THE LOCAL DENSITY OF STATES IN METALLIC NANOPARTICLES: MANIFESTATION ON THE NMR SPECTRA

2005 ◽  
Vol 19 (25) ◽  
pp. 1285-1294 ◽  
Author(s):  
JOSÉ A. GASCÓN ◽  
HORACIO M. PASTAWSKI
Keyword(s):  
Density Of States ◽  
Metallic Nanoparticles ◽  
Local Density ◽  
Scaling Law ◽  
Tight Binding ◽  
Surface States ◽  
Aluminum Nanoparticles ◽  
Binding Model ◽  
Electronic Density ◽  
Knight Shifts

In metallic nanoparticles, shifts in the ionization energy of surface atoms with respect to bulk atoms can lead to surface bands. Within a simple Tight Binding model we find that the projection of the electronic density of states on these sites presents two overlapping structures. One of them is characterized by the level spacing coming from bulk states and the other arises from the surface states. In very small particles, this effect contributes to an over-broadening of the NMR absorption spectra, determined by the Knight shift distribution of magnetic nuclei. We compare our calculated Knight shifts with experiments on aluminum nanoparticles, and show that the deviation of the scaling law as a function of temperature and particle size can be explained in terms of surface states.

SOME FACTORS LEADING TO ASYMMETRY IN ELECTRONIC SPECTRA OF BILAYER GRAPHENE

2011 ◽  
Vol 25 (14) ◽  
pp. 1877-1888
Author(s):  
RUPALI KUNDU
Keyword(s):  
Graphene Layer ◽  
Nearest Neighbor ◽  
Tight Binding ◽  
Energy Difference ◽  
Bilayer Graphene ◽  
Electron Hole ◽  
Binding Model ◽  
Site Energy ◽  
Coupling Parameters ◽  
Electronic Dispersion

We have investigated the effects of in-plane and interplane nearest neighbor overlap integrals (s0 and [Formula: see text]) and the site energy difference (Δ) between atoms in two different sublattices in the same graphene layer on the electronic dispersion of bilayer graphene within tight binding model. We then extended the calculation to include the in-plane next nearest neighbor interactions (γ1, s1) and next to next nearest neighbor interactions (γ2, s2) for bilayer graphene bands. It is observed that [Formula: see text] introduces further asymmetry in energy values of top conduction band and bottom valence band at the K point in addition to the asymmetry due to Δ. In general there is noticeable electron–hole asymmetry in the slope of the bands away from the K point, and also the changes in band widths due to [Formula: see text] as well as the other in-plane coupling parameters. The density of states of bilayer graphene has also been calculated within the same model.

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