Bug #1580

Envelope task #1438: === Physics ===

Envelope task #1406: == Particle correlations ==

ParticleComposition w/ distructive interference (selection rules not met)

Added by a.glavic almost 4 years ago. Updated about 3 years ago.

Status:ResolvedStart date:08 Aug 2016
Priority:HighDue date:
Assignee:herck% Done:


Target version:Sprint 34


As first step to simulated AF spin arrangements on a square lattice I have tried to duplicate the simple single particle basis by doubling the unit cell parameters and using four particles in the basis.

Expected result:
The same intensity pattern for both simulations within numerical errors.

Actual result:
Different Bragg peak size and intensity as well as half order Bragg peaks that should be forbidden by selection rules.

This is an important issue that will be common for many AFM systems.

py_dot_array_nonmag.png - Simulation 1x1 basis (58.5 KB) a.glavic, 08 Aug 2016 18:00

py_dot_array_nonmag_22.png - Simulation 2x2 basis (77 KB) a.glavic, 08 Aug 2016 18:00

py_dot_array_nonmag.py Magnifier - Script 1x1 basis (2.95 KB) a.glavic, 08 Aug 2016 18:00

py_dot_array_nonmag_22.py Magnifier - Script 2x2 basis (3.31 KB) a.glavic, 08 Aug 2016 18:00


#1 Updated by wuttke almost 4 years ago

  • Parent task set to #1406

#2 Updated by herck over 3 years ago

  • Status changed from New to Sprint
  • Target version set to Sprint 34

#3 Updated by herck about 3 years ago

  • Assignee set to herck

#4 Updated by herck about 3 years ago

  • Status changed from Sprint to Resolved

The problem described actually consists of two unrelated issues:
1) A normalization error in the 2D lattice interference function: this has been solved now
2) The violation of the selection rule: this is more subtle. Because of the way we handle finite-size effects (with a so-called decay function), the two cases considered above are not entirely equivalent. There is a selection rule appearing at exactly the peak positions that should be absent, but around it, there will be scattered intensity. This is a direct consequence of the decay function method and can not be cured ad hoc. The solution would be to provide another mechanism for finite-size effects that does not have this problem.

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