THE CRYSTAL-STRUCTURE OF BIOCL

The crystal structure of BiOCl has been redetermined with 3570 observe d reflections of which 174 were unique measured on a computer controll ed Philips PW 1100 single crystal diffractometer. The structure belong s to the tetragonal space group P4/nmm and the cell constants, obtaine d by a least-squares calculation from direct theta-value measurements on the diffractometer, are a = 3.8870(5) and c = 7.3540(5) angstrom. T he positional and thermal parameters, with anisotropic temperature fac tors, were refined by full-matrix least-squares calculations to a fina l R = 9.17%. Each Bi atom is eight-coordinated by 4 O and 4 Cl atoms a t distances of 2.316 angstrom and 3.059 angstrom respectively thus for ming a decahedron. The faces of the decahedron are 2 rectangles (O - O - O - O and Cl - Cl - Cl - Cl) with sides 3.487 angstrom isosceles tr iangles (four O - Cl - O and four Cl - O - Cl) with sides O - Cl 3.249 angstrom and O - O or Cl - Cl 3.487 angstrom. The decahedra are linke d to each other by a common O - Cl edge along the a and b axes in infi nite layers.