Continuity chords of bands and band structure of semiconducting compounds with TlSe-type structure

All the simple band representations of the space group D/sub 4h//sup 18/ are constructed. Using the concept of band representation and continuity chord, developed by Zak, it is shown that for semiconducting compounds with TlSe-type structure it is possible to extract some useful information about the character of localization of basic functions, belonging to the same band, i.e. in fact about the nature of the chemical bond responsible for the observed band structure. In particular, from the comparison with a calculated band structure of the ternary semiconducting compounds with TlSe-type structure, it is shown that the lower four valence bands correspond to s-states of chalcogen atoms. Two following valence bands correspond to s-states of three-valent cations. Then, a large group of ten valence bands is produced by p/sub z/-states of chalcogen atoms and p/sub x/-, p/sub y/-, p/sub z/-states of three-valent cations. (author)