Franz Werner wrote: > Dear Rietvelders > > Is it in principle impossible to determine the absolute structure from powder > data due to reflection overlap or is there a way via multiple wavelength > diffraction experiments? > > Thanks for your advice.
To determine absolute structure, you need three things: (1) a non-centrosymmetric structure, (2) at least one "anomalous" scatterer, and (3) the differences in intensities between Friedel pairs of reflections, i.e. reflection hkl and reflection -h-k-l. In any diffraction experiment with the wavelength chosen carefully, you could satisfy conditions 1 and 2. Number 3 always nails you in a powder experiment due to the systematic, exact, overlap of hkl and -h-k-l. Larry
