Site Differentiation by Synchrotron Radiation Resonant Scattering:  Case Study of BaZn2Ge2

Resonance scattering was applied for the first time to the class of solids with the AB2X2 stoichiometry. A few members of this family seem to violate the developed rules describing the structure−property relationship, and the source of ambiguity is often the experimental determination of the structure itself. As an example, the newly synthesized BaZn2Ge2 can in principle adopt either the ThCr2Si2 or the CaBe2Ge2 type structures, and conventional diffraction techniques do not allow discrimination between the two structure models. The resonance scattering method shows, however, that BaZn2Ge2 crystallizes in the ThCr2Si2 structure (tetragonal I4/mmm; a = 4.527(2) Å c = 10.555(3) Å, Z = 2), in agreement with theoretical analyses.