breogan
Dear all,
Is there any tutorial about how to use charge flipping in Topas with powder data?
Regards,
Breogan
alancoelho
Hi Breogan
No tutorial that I know of; see however the files in the cf directory
cf-alvo4-pawley.inp
cf-alvo4.inp
cf-alvo4-pawley.inp is the Pawley refinement which creates the file alvo4.a for use in cf-alvo4.inp.
cheers
alan
breogan
Hi Alan,
Thank you very much. These two files are a good starting point.
I have two questions about this files:
1) Where should I establish the limit to remove the low d-spacing reflections (delete_observed_reflections = D_spacing <)? I guess it depends mainly on the specific diffractogram. But are there any upper or lower limits?
2) Is there any R factors or error index? Following the manual suggestion I am going to investigate by inclusion/exclusion of keywords and formulas in the input file. But how can I know if I am in the good direction?
Regards,
Breogan
alancoelho
The limit for d-spacing is problem dependent; at a guess most structures can be solved with a limit of 0.8Angstroms and removing lower d-spacing may be beneficial for speed reasons.
The R-factor is: Sum( |Fobs^2 - Fcalc^2| ) / Sum( |Fobs^2| )
Run a few examples in the cf directory to see the behavior.