Dear All:
I have prepared single crystals of Hg(II) complex, but the R(int) was a bit high because the crystals were thin, so could you please recommend a method to increase the thickness o f the crystals.
Best, Adnan
Dear Adnan,
you may use a different solvent/solvent mixture for the crystal growing process.
BR
Guido
Hi Adnan,
There is no such direct effect of R(int) on the thickness of the crystal. Probably quality of crystal (single) is an issue in your case. Also, you check all parameters before integration/ scaling of data. Sometimes, problem of absorption could be a factor (you have Hg) for high R(int). All the best!
Dear Adnan Qadir as mentioned by Guido J. Reiss the most promising way to perhaps grow more compact single crystals is to try crystallization from a different solvent or solvent mixture. My personal favorite in this respect is acetonitrile. If your complex is soluble in this solvent it might be worth a try. Please also see this potentially useful article entitled "How to Grow Single Crystals for X-ray Analysis by Solution Crystallisation"
https://community.dur.ac.uk/crystallography.group/imagesgroup/GrowCrystals.pdf
If you have a batch of many too small single crystals, you could try to perform temperature fluctuations around your average temperature (very often, but always only a few degrees). Because the surface energy term increases especially the energy content of small crystals, they will preferably dissolve upon the small heatings. Then, during cooling, crystallization will happen preferably on the surface of the crystals that are already a bit larger. This process is called Ostwald ripening: https://en.wikipedia.org/wiki/Ostwald_ripening
You have received many good answers to increase thickness , but I would like to examine the crystallography side of this problem. What are the exact dimensions of your crystal? What is your diffractometer (x-ray source and detector)? Exactly what is your Rint? What software are you using? Hg is clearly a large absorber and so absorption correction would clearly be an issue, but much software can do a good job even with very good results.
Dear Adnan Qadir with the so-called "Ostwald ripening" Detlef Klimm mentioned an interesting point. It just requires some patience. Occasionally my co-workers leave their flasks with small crystals in the mother liquid sit on the window board for weeks undisturbed. Often they find that some crystals grow, while the smallest ones redissolve. Please also see the following article entitled "Ostwald ripening with size-dependent rates: Similarity and power-law solutions" which is available as public full text on RG:
Article Ostwald ripening with size-dependent rates: Similarity and p...
Dear Adnan Qadir I fully agree with Joseph S Merola in that you should discuss this problem in detail with your crystallographer. Crystals containing very heavy Hg atoms should diffract quite well. If you have e.g. needle-like crystals, a diameter of ca. 0.1 mm could be sufficient. Types of crystals which crystallographers normally don't like are very thin plates or feather-like crystals.
I discussed the problem [(R(int) = 0.139] with the crystallographer. He stated that
it is related to crystal nature and that the crystal (thin plate) melts when exposed to X-ray for a long time, but he said that the structure is publishable.
Dear Adnan Qadir many thanks for providing this information. It's definitively good news to hear that your crystal structure can be published. You can still try one or two different solvents in order to perhaps obtain more compact crystals. Good luck!
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