When building up structures and finding missing atoms using GSAS, it can be very useful to automatically add the Fourier Peaks into Disang. Most of the peaks provided in the Fourier searching are spurious so it can require great care and tenacity in figuring out which are the real peaks. Using Disang with the GSAS Fourier Map options can greatly assist in finding missing atoms during powder structure refinement.

In GSAS (or EXPGUI) run EXPEDT and then do: Y ( Create a copy of this file and edit it) D (Distance/angle calculation set up) D (Edit the distance/angle routine controls) F (Change the Fourier peak inclusion option) When prompted, type Y (Yes) that you want to include Fourier Peaks in the Disang calculations. Then answer all the questions (maximum peak value to use, minimum peak value to use, Fourier Peak distance radius, etc) Done. Now exit out of EXPEDT and continue on with the refinement and Fourier Maps.

First run a Fourier Difference map, then run FORSRH Fourier Map peak searching. When prompted, add the Fourier Peaks to the GSAS EXP file. Now on running Disang, the output will tell you which peaks are too close to existing atoms based on the distance values you added into the EXPEDT "Fourier peak inclusion option" and will not include them in the calculations. The remaining peaks will then be part of the bond length and angle calculations based with their peak height as the "atom label".