Periodic Boundary Conditions

[Sebastian Calderon]

Dear Prof. Koch,

I have been using QSTEM for STEM / TEM simulation of nanoparticles (supported on amorphous carbon or in vacuum) and I correlate the simulations with experimental results. I got decent correlations, however, I end up with some doubts. 

1. How can I ensure the periodic boundary conditions if I want to generate the TEM or STEM image for the full particle?. 

2. Can I consider the surface of the nanoparticles to be calculated accurately?

3. Is it accurate to simulate the STEM images of amorphous materials using this multislice method?

My questions arise because I read in Advanced Computing in Electron Microscopy Book that "If the slices do not obey periodic boundary conditions in the x and y direction serious artifacts may be generated in the image due to the so called wrap around error". However, I found a paper that cites QSTEM as "HAADF-STEM image simulations are performed with the QSTEM image simulation software (V2.22), which was designed for obtaining quantitative HAADF-STEM images that include the effects of thermal diffuse scattering and inelastic scattering. This software uses the multislice simulation technique which is required for the non-periodic system studied in this work"

Below you can see an example of one of the models that I use. 

Thank you in advance, 

Sebastian 

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