STRUCTURE CHARACTERIZATION WITH NEUTRON POWDER DATA OF LAGAO3 AND NDGAO3 BASED ON X-RAY SINGLE-CRYSTAL DATA - EVIDENCE FOR AN INVERSION CENTER

From neutron powder diffraction intensities it is often problematic to distinguish between centrosymmetry and non-centrosymmetry. X-ray sing le crystal diffraction may be more accurate. In this paper we compare refinement results of crystal structures on the basis of neutron powde r data of orthorhombic NdGaO3 (300 K) and of rhombohedral LaGaO3 (573 K), obtained from non-centrosymmetric and centrosymmetric starting mod els. By using of X-ray single crystal measurements, the structures of LaGaO3 and NdGaO3 could be determined as being centrosymmetric corresp onding to the space group R (3) over bar c and Pbnm, respectively.