query about STEM simulator Detector angles

[seto77]

query about STEM simulator Detector angles

[seto77]

Thanks for asking the question.

Is there any rule on minimum inner detector radius with respect to the convergence angle?

No, there are no specific rules.

If the elastic STEM image is completely dark, the number of diffraction waves considered in the calculation may not be sufficient.

Especially for crystals with low symmetry, the diffraction waves are limited to low-angle regions. If the number of diffraction waves is increased, so that diffraction waves at high angles are also included in the calculation, a proper image will be displayed. (However, it is recommended that the number of diffraction waves be limited to about 200 at most, since the computational cost explodes as the number of diffraction waves increases.)

If the TDS-STEM is also completely dark, check the value of the Debye-Waller factor.

If the Debye-Waller factors for all atoms are zero, then there is no TDS contribution and the TDS-STEM is always dark, regardless of the detector angle value.

Usually, above 79mrad, the TDS contribution will be dominant over elastic scattering. If you do not know the exact value of the DW factor, set B=0.5 for all atoms for now and recalculate the TDS-STEM. I hope it will work.

[sandhok]

Thank you for your response. The information and suggestions you mentioned solved the issue.
Very grateful for your kind reply!