CRYSTAL STRUCTURE OF AgGa2Se3Cl(Br) COMPOUNDS

For the first time, the crystal structures of new quaternary compounds were studied by the powder method. They crystallize in tetragonal system, Sp.Gr. I-4, structural type CuIn2Te3Cl, with cell parameters: AgGa2Se3Cl (a = 5.9789(3) Å, c = 10.8592(7) Å), AgGa2Se3Br (a = 5.9767(3) Å, c = 10.8558(7) Å). From the analysis of the crystal structure it was found that the researched quaternary compounds belong to semiconductors with the general formula AІВІІІ2XVI3YVII (AІ – Cu, Ag; ВІІІ – Ga, In; XVI – S, Se; YVII  Cl, Br, I). Chalcohalide compounds of the АІСІІІ2XVI3YVIІ type refers to cation-defective compounds with a ratio of cations to anions 3:4. Their compositions can be represented by the formula Kn-uuAn, where K cations,  vacancies, A anions, u the first letter of the word unoccupied. For these compounds VEC = 4,571. If we consider the vacancy as an atom with zero valence, we get for compounds АІСІІІ2XVI3YVIІ VEC = 4. This structure refers to the tetrahedrals when the cations are surrounded by the four nearest anions. This is confirmed by the studied crystal structures of the compounds AgGa2Se3Cl(Br). The semiconductor properties can be expected from these and other compounds from the group AІВІІІ2XVI3YVII (AІ – Cu, Ag; ВІІІ – Ga, In; XVI – S, Se; YVII  Cl, Br, I).