Dear Jie, It also depends on whether you believe the SO4 sits with its internal two-fold along the crystal's two-fold axis. If it does you should probably have a 0.5 occ sulfur and two 1.0 occ oxygen atoms. If the symmetry is not obeyed you will have to have four 0.5 occ oxygen atoms.
Be careful, some refinement programs will not be able to handle the bond length and angle restraints if you only supply two oxygen atoms. They will not allow bonds between atoms and symmetry images of atoms. If you are using such a program you will have to supply four oxygen atoms even if this is not what you would otherwise do. Dale Tronrud Charlie Bond wrote: > Hi Jie, > Depending on your resolution, you may be forced use to use S(0.5) and > 4x(0.5) in order to restrain the SO4 to stay tetrahedral in refinement. > Cheers, > Charlie > > > Jie Liu wrote: >> Dear all >> >> I have a sulfate ion sitting on a 2-fold axis. Should I put in pdb file >> one S atom with occu=0.5 and two O atoms with occu=1, or should >> I put one S and four O atoms all with occu=0.5? >> >> Thanks for your inputs. >> >> Jie >> >> . >> >
