I know many scientists claim that they succeeded in measuring atomic spacings down to a few picometres using ultrahigh-resolution electron microscopy. Is there a proof that what they got is not just a reflection or interaction of any sort with excited atoms? This sort of measurement is vital to find out directly many physical parameters determining the properties of matter.
Wikipedia and Google are our friends.
https://en.wikipedia.org/wiki/High-resolution_transmission_electron_microscopy
https://www.google.com/search?q=hrtem+lattice+spacing&rlz=1C1OPRB_enUS553US553&espv=2&biw=1480&bih=926&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwiYpKvU27HNAhUT0WMKHY6UA-sQsAQISQ#imgrc=_
Wikipedia and Google are our friends.
https://en.wikipedia.org/wiki/High-resolution_transmission_electron_microscopy
https://www.google.com/search?q=hrtem+lattice+spacing&rlz=1C1OPRB_enUS553US553&espv=2&biw=1480&bih=926&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwiYpKvU27HNAhUT0WMKHY6UA-sQsAQISQ#imgrc=_
Thank you all. I've many comments, but I wait for more answers. Let's think about all these GRADED GREY SPHERES . Are these really atoms? or excited atoms? or what exactly?
That is good question, Muhammad. To be exact, without compare HRTEM image with simulation no one can say what is atom and what not. If you look at one of my images above you can see designated positions of Si and N atoms. I used multi-slice simulation method. For this purpose several HRTEM images of one place with different objective focus are needed. The next step is comparison of real defocus image series with simulated defocus series. The goal is to find matching of both real and simulated images. However there are many input data which are required by software, e.g. sample thickness, zone axis of oriented crystal, microscope technical data, actual observation settings of microscope optics, and so on.
There are also others simulation methods based on calculations but up to now I am not familiar with them. Nevertheless, for serious HRTEM analysis you always need simulations. If you see beautiful gray spheres you can expect that they should be individual atoms with the same probability as the space between them. And sometimes you can get from microscope HRTEM image with small bars instead of spheres. In such an case it is absolutely imposible to determine exact atomic posiitions without simulations.
Standard TEM image may be misleading for interpretation, but HRTEM image doubly.
Yes, that's why contrast transfer function (CTF) is important. When in "Scherzer defocus" conditions, the HR-TEM image represent "real" atomic positions...
Thank you
I agree, these images illustrate the interatomic distances. This information does not amaze me, remember the old Bragg diffraction experiments. When X-rays (or neutrons) are incident on an atom, they make the electronic cloud move and expand in space . The excitation of electrons re-emit waves with the same frequency (in case of elastic Rayleigh scattering), as blurred spheres. Imagine what happens, in the case of high energy excitations and the nonlinear interaction. I still wait for ore answers, though I appreciate the valuable answers sent so far
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