NEUTRON AND ELECTRON-DIFFRACTION STUDIES OF ZNGA2SE4

ZnCa2Se4 is a II-III-VI compound semiconductor with a zincblende struc ture basically. Convergent-beam electron diffraction (CBED and neutron diffraction were applied to determine its crystal structure unambiguo usly. A CBED pattern clearly exhibits 4(R)mm(R) symmetry, which sugges ts that ZnGa2Se4 belongs to space group I(4) over bar2$ m. Rietveld an alysis of neutron powder diffraction data on the basis of this space g roup shows that the 2a site is fully occupied by Ga and that the 2b si te is completely vacant. On the other hand, the 4d site is statistical ly occupied by Zn and Ga atoms. (C) 1998 Elsevier Science B.V. All rig hts reserved.