Spherical harmonics preferential orientation corrections and structure solution from powder diffraction data - a possible avenue of last resort

Structure solution from powder diffraction data, from either real- or reciprocal-space methods, has generally been thought to require reliable relative intensities to yield a successful solution. An approach is described here which requires no input of the orientation direction when using simulated annealing. The simple addition of a keyword already present in the TOPAS macro language is all that is required to stabilize what otherwise seems like a guaranteed way to destabilize simulated annealing. A recent example with a simple molecular material showed that it is possible, but the more complicated example of triclinic 1A-wollastonite is used to demonstrate that the approach may be more generally applicable. The approach will not work in all cases, but may provide a possible approach of last resort for problems which might otherwise resist attempts at a solution.