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.