I have detected five-fold symmetry in the texture of a monoclinic growth structure. We think it's probably due to twinning. I can't find the twinning relationship (lattice planes etc.) to describe it, though. Does anyone have an idea or the ability to help?
Did you suspect quasicrystals or other type of aperiodicity? Why not?
It might be multiple twinning, check e.g.
http://www.mpi-halle.de/mpi/publi/pdf/5278_04.pdf
Sounds interesting.. it is difficult to contribute with ideas without knowing more details.. how did you detect it, and what material is it ect. But I understand if like to not share it in public :)
Did you analyze you crystal by HRTEM to see the structure of the grains? There you should see clearly the multiple twins and their change in crystallographic orientation.
It could be a qusycrystal, obtained with a rapid cooling (growth). Try to growth with slow cooling and you should get the standard estructure
I would guess you have a 99% chance (not to say 100%) of a fiveling twin. A good example of this is the mineral pentagonite (hence the name!) a Ca, V silicate similar to cavansite (a name suggestive of its composition, in this case).
Twinning could be obtained, as in the case of pentagonite, by reflection on the (110) plane whereby the b axis is turned through an angle of 72.68° closely approximating the internal angles of the pentagon.
An accurate study of the crystal structure should provide you with the structural reason, at the atomic level, for the curiosity at hand.
It's tough to tell without seeing an image. Do you have one to share?
Hi, check this, maybe it helps:http://www.nature.com/nmat/journal/v2/n2/abs/nmat815.html
Multiple twins with fivefold symmetry were observed for the monoclinic Al13Fe4 and Al13Co4 Phases. One Paper is "Multiple Twins of Monoclinic Al13Fe4 Showing Pseudo-Orthorhombic and Fivefold Symmetries" by Ma, Liebertz and Köster:
http://onlinelibrary.wiley.com/doi/10.1002/pssa.2211580203/pdf
The other paper is "Multiple twins of τ2-Al13Co4 showing fivefold symmetry" by Ma and Kuo:
http://link.springer.com/article/10.1007%2FBF02649074
They also explain how they think the twinning works.
First: It is worth knowing if the texture you observed is a surface pattern (growth or dissolution). In this case the pentagonal symmetry should be compatible with the mirror symmetry of all the( h0l ) faces.
Second: Are you sure that the five-fold symmetry is perfectly regular ?
Third: Would you like send me a picture of the "object" you observed?
Thanks for your attention
Dino Aquilano
It seems that an answer I posted yesterday did not take the right way. I was saying that, as already noted in previous answers, more info is necessary.
Dear collegues, thank you for your answers so far. I am sorry for not providing further data at this point. Please undertstand that I need the agreement of my collegues to proceed.
What do you mean with "I have detected" ? Optically, SEM, TEM ? the term you used " monoclinic growth structure" should be explained with a drawing, for instance. Then, I will be able to help you.
Sincerely yours
The five fold symmetry occurs in the texture calculated from an EBSD-scan covering a multicrystalline growth structure of ca. 100 µm in diameter, i.e. SEM-based analysis. The growth of the monoclinic phase was hindered by a system of crystals (5-10 µm) allready present in the matrix. We observe ten poles in the 201-pole figure. It shows ten prefered orientations in the rotation arround the more or less allighned 001-direction. Personally I think it is caused by microtwinning, however I do not know how to prove this.