Modal Orientations on PDF

[Camilo Garzón]

Hi,

I have a doubt that could be a little more theoretical than a software doubt.

Should modal orientations be located in the same place than the maximum intensity points on an Orientation Distribution Function or Pole Direct Figure?

From my point of view, I think that should be in this way due to the orientation with more frequency of a set of data of an EBDS must be represented by a pole in a PDF, isn't it?

That also means that this point should have a bigger intensity than other points in this representation, right? Or Am I wrong in the definition of modal orientations?

I attached are two PDF generated in base a EBSD data of alpha phase of titanium alpha.

The annotations corresponding to the first modal orientations 

I calculated the modal orientations and the weight in this way:

[modesa,weights] = calcComponents(odfa)

And plot in this way

plotPDF(odfa,h,'upper','projection','eangle','contourf','minmax')

CLim(gcm,'equal')

mtexColorbar

annotate(modesb(1),'marker','s','MarkerSize',8,'MarkerFaceColor','k');

annotate(modesb(2),'marker','s','MarkerSize',8,'MarkerFaceColor','y');

annotate(modesb(3),'marker','s','MarkerSize',8,'MarkerFaceColor','g');

annotate(modesb(4),'marker','s','MarkerSize',8,'MarkerFaceColor','m');

I don't understand, why are points over empty spaces?

Thanks for your help

[Rüdiger Kilian]

Hi,
using calcModes or calcComponents gives you local maxima on the odf. However, this does not mean that those will end up on maxima on all pole figures simulateously. An odf can be a mixture of different components and such will be the densities represented in pole figures. This means the position of maxima in different pole figures need not obey crystal symmetry if the underlying odf is derived from multiple orientations. However, the point you plot on top of the polefigures which you derived from a single orientation (representing a local maximum in the odf) of course mut obey crystal symmetry.

I hope this helps.
Cheers,
Rüdiger
________________________________________
From: mtex...@googlegroups.com <mtex...@googlegroups.com> on behalf of Camilo Garzón <scga...@gmail.com>
Sent: Thursday, May 16, 2019 4:48:04 AM
To: MTEX
Subject: {MTEX} Modal Orientations on PDF

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[MTEXrulez]

Hi

would those maxima coincide with the maxima on the pole figure (like in the nice example of Camilo Garzón) if he would use

[modes,values] = calcModes(calcODF(oris,'exact'),n);

instead?

Best Regards,

Michael

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[ruediger Kilian]

No,
it has nothing to do with the way of computing the local maxima but it is due to the nature of the relation between odf and poelfigure.

Cheers,
Rüdiger

[Camilo Garzón]

Hi Rüdiger and Thanks again.

Your explanation is pretty clear, so It means that If I plot the ODF with the phi2 that corresponds to the maximums each modal orientation must coincide with them, right?

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