Extract Nye's tensor component from Ovito

[toninegi01]

Hi Alex,
I have few questions related to Ovito. I have installed Ovito 2.9.0 in windows.

1) Is it possible to extract Nye's tensor components from the available list of modifiers? My best guess for relevant modifiers are 'Elastic strain calculation' and 'PTM'.

2) I tried to visualize local lattice orientation using python code example (https://ovito.org/manual/python/introduction/examples.html#example-visualize-local-lattice-orientation).
However, when I run the script in the example after adding it using 'python script' modifier, the color doesn't change. The PTM modifier is working fine as new variables related to orientation are available.
A screenshot is attached for reference.

Thanks and Regards
Anuj Bisht

P.S: I have not installed python and numpy separately.

[Alexander Stukowski]

Hi Anuj,

1)

Both the Elastic Strain Calculation and the PTM modifier can compute the atomic elastic deformation gradient tensor F. This is, if I remember correctly, the inverse-transpose of the lattice correspondence tensor G mentioned in the original publication of Hartley and Mishin [Acta Materialia 53 (2005) 1313]. The Nye tensor is the negative curl of this G tensor, which must be calculated using a finite differences scheme. OVITO doesn't do this last step for you, sorry.   

2)

I think you didn't copy/paste the complete script from the example page. The implementation of the modify() function in your screenshot is obviously incomplete.

-Alex

[toninegi01]

Hi Alex,
Thank you for replying so soon.

1) I will try to compute the Nye tensor from the G tensor as reported in the indicated paper. Thank you.

2) I pasted the full script present in the example in the script window (screenshots attached). After that I have pressed the play (green) button. However, no output appears in the script output window. Is there addition steps required for the implementation of the modify() function ?

Thanks and Regards
Anuj   

[Alexander Stukowski]

My apologies, this time it wasn't your fault. The last (and essential) code line was missing from the old version of the Python documentation. Here is the current version of the manual, where the error has been fixed:

https://ovito.org/manual_testing/python/introduction/examples.html#example-visualize-local-lattice-orientation

[toninegi01]

Yes, it is working with the updated script.

Thank you!!