Density functional theory tight-binding

Electronic io- -io-5 Emission and absorption spectra photoelectric effect electric, magnetic, thermal properties of solids The Schrodinger equation pseudopotentials density functional theory tight-binding approximation embedded atom method... 

AMI Semiempirical Austin method 1 CSA Conformational space annealing DFT Density functional theory DFTB Density-functional-based tight binding EA Evolutionary algorithm... 

Zhechkov L, Heine T, Patchkovskii S, Seifert G, Duarte HA (2005) An efficient a posteriori treatment for dispersion interaction in density-functional-based tight binding. J Chem Theory Comput l(5) 841-847. doi 10.1021/ct050065y... 

W. M. C. Foulkes and R. Haydock, Tight-Binding Models and Density Functional Theory, Phys. Rev. B 39 12520 (1989)... 

In this paper we present preliminary results of an ab-initio study of quantum diffusion in the crystalline a-AlMnSi phase. The number of atoms in the unit cell (138) is sufficiently small to permit computation with the ab-initio Linearized Muffin Tin Orbitals (LMTO) method and provides us a good starting model. Within the Density Functional Theory (DFT) [15,16], this approach has still limitations due to the Local Density Approximation (LDA) for the exchange-correlation potential treatment of electron correlations and due to the approximation in the solution of the Schrodinger equation as explained in next section. However, we believe that this starting point is much better than simplified parametrized tight-binding like s-band models. 

Preliminary models of the surface topography, for example, can be determined by atomic-probe methods, ion-scattering, electron diffraction, or Auger spectroscopy. The chemical bonds of adsorbates can be estimated from infrared spectroscopy. The surface electronic structure is accessible by photoelectron emission techniques. In case the surface structure is known, its electronic structure has to be computed with sophisticated methods, where existing codes more and more rely on first principles density functional theory (DFT) [16-18], or, in case of tight-binding models [19], they obtain their parameters from a fit to DFT data [20]. The fit is not without ambiguities, since it is unknown whether the density of states used for the fit is really unique. 

The LCAO tight-binding (Hartree-Fock) method and its successor, the density-functional theory (DFT), were used originally to solve electronic structure problems. More recently, both have been applied to the calculation of total energy, which includes contributions due to core-core, core-electron, and electron-electron interactions. By varying the coordinates of the core, the dependence of the total energy on the core coordinates can be examined. This is referred... 

The definition of the concept ab initio is somewhat fluid, but usually means essentially free of empirical parameters. Being ab initio is generally considered a quality stamp, but one should be aware that some approaches, which ru e formally parameter-free, e.g. Thomas-Fermi density functional theory or ab initio tight binding, fail miserably outside limited application ranges. 

Figure 5. Molecular modeling methods at various scales. MO-miolecular orbital DFT-density functional theory TB-tight binding QM/MM-4iybrid quantum mechanics/molecular mechanics MD nolecnlar dynamics.

Porezag D, Frauenheim T, Kohler T, Seifert G, Kaschner R (1995) Construction of tight-binding-like potentials on the basis of density-functional theory application to carbon. Phys RevB 51 12947-12957... 

Fig. 4.15. Band structure for Mo as obtained from tight-binding calculations and from density functional theory (from Mehl and Papaconstantopoulos (1996)). The notation F, N, H, etc. refers to particular i-points within the BriUourn zone.

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