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The exercise discussed here is designed to put you into the shoes of a scientific detective. Using a simple electron microscope simulator, which at the moment uses a Java applet and hence may not be mobile-friendly, you'll be looking at the world on size scales where thermodynamic disorder lives, where chemistry takes place, where biological emergence & the miracle of cooperation between eukaryotic cells is found, and where nanotechnology in the days ahead will expand its touch of our everyday lives.
Electrons accelerated through 300,000 Volts have wavelengths near 2 picometers and can be focused by magnetic lenses so that one can image individual atoms with them. In this applied modern physics problem you try to measure the distance between specimen atoms in a simulated electron microscope, and to determine the number of nearest neighbors for those atoms as well.
Begin by zooming in and around on the tiny disk that you'll find in the virtual microscopes that you can find here or here. Feel free to assume the disk diameter is 3mm, and to use the superposed grid to help estimate sizes of smaller things. The field-width estimator can also be used, although this might add additional uncertainty to your measurement. Then do the best you can to determine the spacing between gray atoms in the specimen's disk, a few of which are visible if you zoom in enough to see them.
1. In your project notebook, describe your approach to determining the distance between atoms and any numbers that you generated in the process.Sample Response: Zooming in until the 3mm disk filled the screen sideways, the button field-width-estimate said 2.8mm. Thus I assume that this field-width-estimate should be multiplied by about 3/2.8~1.07. I then zoomed in until the field width estimate was about 20nm, and hit the substrate button to center the grey atom region. Finally I zoomed to a field width estimate of 3.12nm and tilted until I could see two adjacent atoms perpendicular to my view. On my computer screen they were 1.9cm apart on a 10.2cm wide window, suggesting that the atom separation was (1.9/10.2)*1.07*3.12nm~0.62nm or 620 picometers. Doing this several times gave me values between 590 and 625 picometers. Tilting around also indicated that bulk atoms in this stuff will have 8 nearest neighbors at corners of a cube.
2. How many nearest neighbors do you figure that the grey atoms in the specimen have, i.e. what is their kissing number in 3D?
3. I estimate that the distance between each grey atom and its nearest neighbors is about how many picometers?
4. My uncertainty in the above distance estimate is how many picometers?
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