I am trying to figure out the maximum and minimum interplanar distance I could determine with 8keV in XRD. I assumed that, following the Braggs Law, the maximum d_hkl would be around 0.077nm (2theta=180 degrees) but I would like to know which is the minimum 2theta angle which can give rise to the maximum d_hkl...
The energy of the photons, or in other words the wavelength, is of secondary importance, if you're asking for the interplanar distance. 8 keV means that you have the copper tube (0.154 nm wavelength). Bragg's law determines the relationship between interplanar distance (d_hkl), reflection angle (theta) and wavelength (lambda). For a given lambda you may calculate the pairs theta - d_hkl. Now, depending on the theta (or 2 theta) angle range available in your diffractometer, you can calculate the observable d_hkl distances. For examples (copper tube assumed), if the minimum 2 theta angle in your diffractometer equals 10 degrees, the d_hkl will be of 8.83 A.; for 2 theta = 5 degrees the d_hkl will be of 17.6 A. The smallest detectable d_hkl will also depend on the 2 theta of your equipment, and for 140 degrees the d_hkl will equal to 0.82 A, or for 160 degrees the minimum d_hkl will be of 0.78 A. As you see, your question may be answered only by you, because it is you who can determine the equipment's minimum and maximum 2 theta values. Last, but not least, if you have a diffractometer in front of you, try to imagine where the detector will be if you move it to 2 theta = 180 degrees. I guess it will be exactly between the tube and the sample. Will it work then?
The energy of the photons, or in other words the wavelength, is of secondary importance, if you're asking for the interplanar distance. 8 keV means that you have the copper tube (0.154 nm wavelength). Bragg's law determines the relationship between interplanar distance (d_hkl), reflection angle (theta) and wavelength (lambda). For a given lambda you may calculate the pairs theta - d_hkl. Now, depending on the theta (or 2 theta) angle range available in your diffractometer, you can calculate the observable d_hkl distances. For examples (copper tube assumed), if the minimum 2 theta angle in your diffractometer equals 10 degrees, the d_hkl will be of 8.83 A.; for 2 theta = 5 degrees the d_hkl will be of 17.6 A. The smallest detectable d_hkl will also depend on the 2 theta of your equipment, and for 140 degrees the d_hkl will equal to 0.82 A, or for 160 degrees the minimum d_hkl will be of 0.78 A. As you see, your question may be answered only by you, because it is you who can determine the equipment's minimum and maximum 2 theta values. Last, but not least, if you have a diffractometer in front of you, try to imagine where the detector will be if you move it to 2 theta = 180 degrees. I guess it will be exactly between the tube and the sample. Will it work then?
Thank you very much for your answers!
Also, thank you very much for all the explanation Jarosław Ferenc . Everything is more clear now.
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