I have a single crystal structure that should be solved in Orthorhombic (Ima2) space group (suggested by Platon). But I am not able to see the structure at all in this symmetry. However same data was solved (R-value = 3%) in the triclic symmentry.
I am facing this problem with different datasets for a particular MOF crystal.
Please help.
This occasionally happens. It should be carefully checked, whether the crystal structure solved and thus refined in triclinic symmetry has hidden symmetry elements. Then it is imperative to re-refine the structure in higher symmetry (you do not need to solve the structure to do a refinement, but you can also simply insert a derived/known structure!). If then the refinement in higher symmetry gives not significantly poorer residuals, you should regard it to be of the higher symmetry, irrespectively of the fact that the structure solving algorithm had been unsuccessful in the higher symmmetry. Note that also Ima2 is a valid but for many systems unusual space group. Check for presence of more symmetry elements, e.g. for space groups of the crystal class mmm. In my opinion careless publication of structures with too low symmetry not cleary evident from the diffraction data or from other good information is poor practice.
Hi,
if you solved it in lower symmtry. open the res file in platon, then search for higher symmetry using addsymm command "triangle icon" . Then use "addsym shelx command under Publish list. in this way new res file will be generated by Platon with higher symmery and you are done
Dear Himan Dev Singh .
If I don't see the raw data it's complicated to discuss the symmetry of a weighted reciprocal lattice in detail ... but I should add some general comments.
1. For MOF compounds and coordination polymers it is well known that the approximate structure is dominated by the framework even though the molecules within the voids sometimes break the symmetry.
2. The fact that inclusion compounds often face a reduced symmetry is well documented (For example: by us and many others).
3. The molecules located in voids may slightly affect the symmetry of the host framework.
4. I don't know if your dataset have been "squeezed" (DOI:10.1107/S2053229614024929) by Platon.
5. If the "squeeze-algorthim" was used, the aforementioned deviation of the framework from higher symmetry may be still present.
Finally: Andreas Leineweber is right. Ima2 is not a very "popular" ;) space group.
Best regards
Guido
Hi Himan,
Two suggestions in addition to above mentioned answers:
1. Carefully check systematic absences
2. You can manually put the suggested space group (considering small unit cell for orthorhombic) prior to ins generation and then try to solve it.
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