Polyhedral template matching problem for unitcell diamond

Dear Ovito team,
I’m using Ovito to identify diamond structure of CdTe. For the unitcell, all atoms are assigned with ‘Other’. However, if I use a large supercell, all are ‘Cubic diamond’. Is that a bug?

Yours sincerely,

Could you please upload the unit cell file? Then I am going to check this.

unitcell_CdTe (702 Bytes)
Hi, this is the unitcell. If you enlarge this to get a supercell, everything’s OK. Thanks.

You are right, the PTM algorithm fails to identify diamond structures if multiple periodic images of the same atom appear in the second neighbor shell of the central atom to be identified. This is the case for the small unit cell.

I’m not sure if there is an easy fix for this limitation. Peter Larsen, the author of the PTM algorithm used by OVITO, probably accepted this limitation for the sake of performance, which matters more for large simulations. I am going to ask him about it.

As you’ve mentioned, one workaround is to explicitly extend the unit cell using OVITO’s Replicate modifier, for example. Or to use the Identify Diamond Structure modifier instead of PTM, which doesn’t have this kind of limitation.

Thank you! I may use these workarounds instead.