Also try BALBES from the York site supplying the high symmetry data
and let it check things for you.
Sent from my iPhone
On 3 Jan 2009, at 14:40, James Holton <[log in to unmask]> wrote:
> You should pick your free-R set in C2221 and then symmetry-expand it
> to C2. Otherwise, every hkl in your "free" R set will have an NCS
> "mate" in the working set, and using NCS restrains will completely
> invalidate the free R analysis. That is, your free-R will be
> essentially equal to the regular crystallographic R and it will be
> possible to take a completely wrong MR solution and refine it to an
> "acceptable" free R, and if you do that, we will all make fun of you.
>
> -James Holton
> MAD Scientist
>
> 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!
>>
>>
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