Semiempirical Tight Binding Research Articles

The reliability of the semi-empirical tight-binding method for band structure calculations

An analysis is given of the behaviour of two-centre parameters used in the semi-empirical tight-binding method, as a function of inter-atomic separation, and for various values of the principal atomic quantum numbers. It is found that, in certain cases, the use of free atom wavefunctions to calculate these parameters can lead to their nonphysical behaviour. Numerical calculations are presented which show when this problem occurs and an example demonstrates that it can be a problem in actual calculations. Various methods to overcome this difficulty are discussed. A modification of the semi-empirical tight binding method is given which eliminates the nonphysical behaviour of the parameters, and makes it possible to perform detailed band calculations using suitable localized functions.

The band structures of some transition metal dichalcogenides: band structures of the titanium dichalcogenides

Band structures of the stoichiometric titanium dichalcogenides TiS2, TiSe2 and TiTe2 are calculated using a semi-empirical tight binding method. The results are fitted to optical reflectivity and absorption data and are compared with similar calculations on other group IVA dichalcogenides.

The band structures of some transition metal dichalcogenides. III. Group VIA: trigonal prism materials

For pt. II see ibid., vol. 5, 746 (1972). The semiempirical tight binding method is applied to the calculation of the electronic band structures of MoS2, MoSe2, alpha -MoTe2, WS2 and WSe2 in a two dimensional approximation. After a review of the structure and the physical properties of these compounds, the symmetry of the relevant Brillouin zones, including the effects of spin, is discussed. With this material one can fit the calculated band structures of all five compounds to the experimental data. Some of the fine structure of the optical spectra can be interpreted by extending the work into three dimensions. It is also possible to explain some of the properties to which the calculations were not fitted explicitly.

The band structures of some transition metal dichalcogenides. II. Group IVA; octahedral coordination

For pt. I see ibid., vol. 5, 738 (1972). The band structures of some group IVA dichalcogenides-ZrS2, ZrSe2, HfS2, HfSe2-are calculated using a semiempirical tight binding method. A symmetry analysis of the crystal structure is given together with the selection rules for optical transitions. The experimental properties of the materials are reviewed and certain features in the optical transmission spectra are used to fix the values of three parameters used in the calculation. The joint density of states function is computed and the results of this and the band structure calculations are discussed.

Structure of the conduction band in diamond and silicon in the semiempirical tight binding method

Structure of the conduction band in diamond and silicon in the semiempirical tight binding method