Hi. If the most precise and accurate description of your crystal structure is the orthorhombic one, you should average the replicated reflections and refine the structure in C2221. If the crystals are orthorhombic and you refine and report it in C2, you're producing a model that is larger and more complex than you need to explain the experimental data. You're also reporting to the world that the two molecules in the C2 asymmetric unit are different when there's no experimental evidence supporting that.
To extract the most information from your diffraction data, you should refine your structure in the highest symmetry space group consistent with the experimental data. Ron On Sat, 3 Jan 2009, Yu Jiang wrote:
Dear all, I am now refining one structure in space group C2 with 2 molecules, however we find the data can be processed in C2221 with 1 molecule. The questions are: 1. Can I still use space group C2 instead of C2221, even if the two molecules almost have crystallographic symmetry? Should I provide any excuses? 2. Is there any indication or necessity to refine structures in lower space group instead of higher? Many thanks!
