Hi Hailiang,
Yes, I understand it is part of phenix.refine output, but I am wondering whether there is a way to evaluate LLG by only using user-provided structure factor (Fo, sigFo, Fc).
internally in PHENIX there are many pieces of code that do this (like X-ray target calculation in phenix.refine), but I am not aware of any dedicated program that is exposed to the end-user and that does this. So I guess the quick answer is "no". If you think it is important to have then, as I mentioned before, I can and add it to phenix.model_vs_data output.
I think phenix.refine will have to read a PDB file, based on which model Fc will be calculated and used to evaluate LLG (instead of my provided Fc).
This is true. It will have to read a PDB file to obtain Fmodel (which is not just Fc).
I know there is a well-established LLG formula and may write a short code but I need to minimize sigmaA I think which take some efforts:-(
Not sure the code will be short since you have to estimate sigmaA (or alpha/beta - what's used on phenix.refine). By the way, in this case your input will also have to include free-R flags in addition to Fo and Fmodel. I recall I spent more than a week before I got it right and fast -;) Pavel.