X-RAY SPECTROSCOPIC STUDIES OF SOME COMPOUNDS WITH THE SAME CHEMICAL FORMULA AND DIFFERENT CRYSTAL-STRUCTURE

With the x-ray spectroscopy method two groups of semiconducting compou nds are investigated. The first group consists of: CdIn2S4 (spinel typ e structure; (Fd3m-Ok1), CdGa2S4 and HgGa24(the ''defective'' chalcopy rite; (I (4) over bar-S4(2)):). To the second group belong: Tl3TaS4 (t hat is made of coordinative tetrahedra [TaS4] and of structure units [ TIS8]; (I (4) over bar 3m-Td(3))) and isostructural compounds Tl3PS4 a nd Tl4AsS4 (the structural type K3PS4; (pnma-C2h?(16))). The fluoresce nt K-emission bands and absorption K-spectra (XANES) of sulphur in com pounds investigated are received with the resolution about 0.2 eV. The primary L-2,L-3-emission bands of S have been studied using RSM-500 w ith resolution 0.4 eV. The electron energy structure of the valence ba nds are similar in isoelectronic compounds CdIn2S4, CdGa2S4 and HgGa2S 4 that follows from the likeness of the forms of the x-ray emission ba nds in these compounds. At the same time the absorption SK-spectra (XA NES) are alike only for CdGa2S4 and HgGa2S4 and differ significantly w ith SK-spectrum of CdIn2S4, that is due to the difference of S-atom so rroundings in these compounds. The similarity of the forms of all x-ra y spectra in isostructural and isoelectronic compounds Tl3PS4 and Tl3A sS4 proves the likeness of the electron-energy structure in these comp ounds and of the environment of S-atom in these compounds. The emissio n and absorption spectra of S in Tl3TaS4 differ from ones of Tl3PS4 an d Tl3AsS4, that is due to the fact, that Ta-atom is not isoelectronic to atoms of P and As, that results in the difference of S-atom surroun dings and the electron-energy structure.