With polarizing microscope, you probably have single crystal if whole volume of the crystal is going dark or back bright at the same angle of rotation between crossed polarizers.

But sometimes even in such case, diffractometer has different opinion ;)

Try this: http://www.agilent.com/chem/crystalchallenge

(I got 5/10...)

For example you can use the ability of crystal to double the frequency.

Dear Dmitry,

poly crystalline does not used in frequency doubling experiments?

With polarizing microscope, you probably have single crystal if whole volume of the crystal is going dark or back bright at the same angle of rotation between crossed polarizers.

But sometimes even in such case, diffractometer has different opinion ;)

Try this: http://www.agilent.com/chem/crystalchallenge

(I got 5/10...)

I would say most conclusive way is to carry out HR-TEM (+ Selective Area Diffraction if crystals are large enough). I know that people use it regularly to determine whether the solution grown nanowires/platelets are single crystals or polycrystalline. Just be careful with the e-beam induced crystallization and beam damage.

In single crystals you can can see the special direction

TEM can able to give the solution of your problem......contrast variation with dark field mode can give you better understanding about this.....as Kahraman already said that the Selected Area Diffraction pattern (" set the aperture according to the grain size" or one more mode can work here nano diffraction mode) ......can give the single crystal pattern..... only thing you have to do is that ....you have to take the collective information from localize regions.......

You can try HR-TEM.. This is kind of an upgrade or additional attachment that comes with TEM and can help you study individual crystals..

If the crystals are transparent (likely the case of organic crystals, but not necessarily so for organometallic/inorganic) you can use a polarizing light microscope, easily available in a lab at relatively low costs.

For non transparent crystals the problem is more serious, as one need some penetrating radiation to know it. Anyway, a close look at the surfaces under the microscope could also be useful. Crystals normally have clear cut faces (not necessarily nice and easy morphologies). Glassy materials are also reflecting the light, but their surfaces can be somewhat roundish (for example, it often occurs that black spherules are not crystalline).

I do not understand those who suggested TEM: of course it would solve the problem, but if one does not have an X-ray diffractometer at hand, how is it possible that he has instead a TEM (4-5 times more expensive)?

I also do not understand the frequency doubling technique: only a subset of the crystal classes allow frequency doubling, therefore this is not a necessary condition. Moreover, the frequency doubling depends on the type and orientation of molecules in crystals, therefore it might also be that a crystal belonging to a crystal class that allows frequency doubling, does not actually show significant (measurable) signal.

Piero, e.g. our faculty already had TEM for a years until I got the 20 yrs old diffractometer :)

But I perceived that question possibly is about judging the solution grown crystals IN mother liquor (because sometimes crystals can be unstable out of solution) and in such cases TEM is not possible. But with polarizing microsope it is possible.

When you are talking about surfaces - e.g. when some etching lines are visible, single crystals don't exhibit sharp angles between them (e.g. it was shown by such observation that fullerites are not hexagonal, but cubic - DOI: 10.1007/BF00539469).

It is only empirical rule AFAIK, but I don't know any exception.

@Piero Macchi; Sir you are absolutely right that the TEM is more expensive and rare in comparison to the XRD. However, I assumed that the growth of crystals to the XRD friendly sizes, is the problem at hand rather than a lack of the instrument. In most XRD machines, as I'm sure you are already aware, the spot size is in the millimeter range. One information that would come handy here is the size of the crystals of course. I assumed, these solution grown crystals have sizes in the 100 nm range. Otherwise it would require tedious sample preparation for TEM. Last but not least, it seems that there is a high resolution TEM available there at PSG institutions; http://www.psgtech.edu/Nanotechnology.php It turns out that TEM is not as rare as it was before. By the way I do not study TEM, mine is only an opinion.

@Kahraman Keskinbora: I understand the question is: "how to ascertain that you have single crystals from a solution?" Of course one should better define what is a single crystal and what is the critical size to consider it as a single crystal. This is difficult to say and should be clarified by the author of the question.

Anyway, XRD can offer much smaller spot size than what you wrote. A laboratory machine for single crystal can, nowadays, produce a spot size below 100 micron and, at synchrotron station, even below 10 microns. Moreover, samples smaller than this size may also be studied with XRD (the beam spot being only an upper, not a lower limit).

Anyway, my interpretation of the question is: "how can we rapidly ascertain that a singly crystal (and not an amorphous or a poly-crystal) sample has been synthesized, before sending the sample for more accurate but expensive and time consuming analysis?" If this is what Jayaramakrishan meant, then TEM is screened out, because it is expensive, time consuming, not doable for samples that are easily damaged by high vacuum (in particular, not doable while keeping the sample in solution) and not doable by a person without sufficient training and experience.

If the purpose of the question was different, then many comments on TEM presented in this discussion are perfectly sensible and useful.

You are right about the vacuum problem...

As usual the original poser of the question is absconding since November 21st, 2013. The question is incomplete in the definition of the challenge but interesting from a "fundamental" point of view. The more complete the information up front the better the solution proposed by the experts in RG. However, presently due to lack of information our responses are highly speculative.

So, V. Jay! Do you mean, "not polycrystalline agglomerates"? What size are your "particles"? What size do you expect the single crystals to be? Real time Bragg XRD Microscopy would suite your needs very well. We've imaged crystallite sizes ranging from 1-100um and beyond routinely with transmission/reflection mode real time Bragg XRD Microscopy http://www.flickr.com/photos/85210325@N04/7920887956/in/set-72157632728981912. Photographic (Polaroid) film would do the trick too if you knew how. Try it in transmission mode, you'll see. Have fun!

Here is an example of HgMnTe wafers both mono-crystalline and poly-crystalline:

http://www.flickr.com/photos/85210325@N04/8217450281/in/set-72157632724040561

http://www.youtube.com/watch?v=IU0m4yI7D-k&list=PL7032E2DAF1F3941F

BTW it is not the incident beam size that is the limiting factor in most XRD systems. It is instead the detector spatial resolution that is usually the culprit. There are techniques that use X-ray beam divergence to create magnification in order to look at smaller diffracting domains. Sigmund Weissmann et all @ Rutgers have pioneered these methods since the 1950's. Check the literature for details. I'll post references and links when any of you become interested.

I recommend a larger than crystal size beam to bath the entire sample in real space and then "sort it all out in the 2D reciprocal space" (diffraction space) using a high spatial resolution image acquisition tool (dental film does wonders) combined with a versatile & precise sample manipulation mechanism. TEM, SEM etc. are too esoteric a solution for this simple "old as the Braggs" challenge. Most of the pioneering work in XRD was done using film in the past. These days we have the advantage of cost-effective 2D XRD imaging tools readily available.

I suppos to etching of crystals agglomerate into liqud soluvent. It is known that grain boundaries solute faster then body of crystals. So if your agglomerate will decomposes onto single crystals then you have a druse. It is not universal method but very simple and quck. You must not wait finish of process, it is enough to see visualisation of grain boundaries.

You can try to take X-ray diffraction spectrum if it gave a uniform X-ray pattern then it is a single crystal or you may use electron microscope

Hatem! Yes, only in comparison with the incident beam. In other words, using the Berg-Barett approach. This would be a challenge if the crystals were small.

http://www.flickr.com/photos/85210325@N04/8217450281/in/set-72157632724040561

Thank you Ravi

Yes I agree with you .Thanks a good information and notice .I appreciate that

yours sincerely

Hatem Maraqah

Can we say that if the crystal has grown exactly according to habit, there is a probability that it can be single crystal?

@ Manisha Joshi

Yes, I think.

I do it and as a rule it is valid.

Thanks a lot Alexander.

Can you suggest any paper on this for further readings

Thank you all for wonderful discussions on my question which is useful for me to know about lot of things in crystals

@ Manisha,

Yes. If shape of a crystal is perfect (theoretically predicted for a given compound), which is very likely, that this be a single crystal.

@ Alexander,

Indeed, by controlled "etching" the agglomerate of crystals in a solvent, can effectively separate them into monocrystals (not always!). In my experience, however, that this method is best suited for relatively large crystals, which unfortunately not always take place.

@ Manisha Joshi

I recommend to google subject "optical crystallography". These science is in close relation with habitus of crystals.

Thanks to Alexander as well as Andrzej.

Attached the crystal I had doubt. Size is about 5mm in height. Compound is niso4 hydtrate.

XR Laue diffraction could be a better check i.e. if you take two patterns at 180°, they should be symetrical vs the horizontal plane, this will tell you that between your two XR impact point, the orientation matrix is the same ... then do the same in the two other directions and you'll be sure that you get A single crystal.

if your crystal is thin enough, you can save the second shot using transmission geometry.

this can be done in one only shot using neutrons.

I understand that if you have not access to XR laue on films or CCD, neither to a neutron source, it is good to know other techniques like etching or morphological survey (grain limits, // faces ...)

In my knowledge, XRD is the only unequivocal real time in situ NDE technique for confirming the mono-crystallinity of any particle, period!

http://www.flickr.com/photos/85210325@N04/10515372183/

Similar RG discussion: https://www.researchgate.net/post/What_challenges_are_there_regarding_obtaining_a_diffraction_pattern_for_a_particular_compound

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