THE ROOM-TEMPERATURE STRUCTURE OF NDPDSB

We propose a structure for NdPdSb at room temperature (295 K) determined by reverse modeling of X-ray diffraction data using Rietveld methods. The proposed structure has Pmmb (special setting of Pmma) space group symmetry with a unit cell of 4.5833(6) X 7.7189(3) X 7.937(1) Angstrom. One of the salient features of the proposed structure is the separation of Pd and Sb in layers along the a axis. The separation leads to two crystallographically distinct Nd sites. An analysis of the Bragg peak widths indicates that the sample is composed of large crystallites (of the order of a few microns) but that the crystallites are twinned on the mesoscale (twin domains on the order of 1000 Angstrom).