The precision of XRD is reported to be about 0.01A~0.001A. And what is the sensitivity of XRD? Is it same as the precision? Would the change of 0.0001A be measured through XRD?
Sensitivity and precision are not the same. However, the more sensitive the technique the better your chances of improving the precision. I think the reported limit of precision of 0,001 A requires a commensurate significant sensitivity to the compound you are interested in studying. Look up similar compounds in the literature and their XRD can be helpful. While there may be something oput there that I am unfamiliar with , I think it will be very difficult to assess a change of ) 0.0001A.
It should be extremely difficult.
For single crystal measurement, you'll obtain different cell parameters even if you use the same crystal, the same temperature (Cryostream-controlled) and the same strategy for each measurement.
Even obtaining such precise cell parameters is a job for special experimental arrangement (two-crystal diffractometer for example). When I had a series of samples from the same reaction system for screening and eventual measurement of the new structures (it is short, 10 frames screening followed by 30-60 frames preexperiment when in doubt and normal experiment when cell parameters are significantly different or the sample is suspect from any other reason, like colour, morphology, ...), the crystals of the same compound (with certain possibility of some substitution disorders) are not 100% equal - I don't know exactly about this calculation in CrysAlis, it is most possibly based on cell volume, but typical values for the same compound are in the 99.x-98 % range. Thus precision at 4th decimal position is illusory, even if statistics from the cell refinement is claiming so.
If you want better resolution for Hydrogen positions you might consider Neutron diffraction to complement x-ray measurements.
But it will be still well above 0.001 A :) not talking about almost necessary deuteration of the sample due to negative scattering factor of protium and a need of "somewhat" bigger crystals (several milimeters to centimeters with old-fashioned serial detectors, although with modern hardware one milimeter should be good enough)
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