TiGePt - a study of Friedel differences

The X-ray single-crystal diffraction intensities of the intermetallic compound TiGePt were analysed. These showed beyond doubt that the crystal structure is non-centrosymmetric. The analysis revolves around the resonant-scattering contribution to differences in intensity between Friedel opposites hkl and (h) over bar(k) over bar(l) over bar. The following techniques were used: R-merge factors on the average (A) and difference (D) of Friedel opposites; statistical estimates of the resonant-scattering contribution to Friedel opposites; plots of 2A(obs) against 2A(model) and of D-obs against D-model; the antisymmetric D-Patterson function. Moreover it was possible to show that a non-standard atomic model was unnecessary to describe TiGePt. Two data sets are compared. That measured with Ag K alpha radiation at 295 K to a resolution of 1.25 angstrom(-1) is less conclusive than the one measured with Mo K alpha radiation at 100 K to the lower resolution of 0.93 angstrom(-1). This result is probably due to the fact that the resonant scattering of Pt is larger for Mo K alpha than for AgK alpha radiation.