TiGePt – a study of Friedel differences

Abstract

Abstract: 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 \bar h\bar k\bar l. The following techniques were used: Rmerge factors on the average (A) and difference (D) of Friedel opposites; statistical estimates of the resonant-scattering contribution to Friedel opposites; plots of 2Aobs against 2Amodel and of Dobs against Dmodel; 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 Å-1 is less conclusive than the one measured with Mo K[alpha] radiation at 100 K to the lower resolution of 0.93 Å-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.