There are a few rules in crystallography to predict possible band positions. These are only rules since finally the crystal structure (distribution of atoms in the unit cell) decides whether a band becomes visible or not.
If you search for not yet discovered bands, feel free to follow some recommendations:
- Look for intersections between strong poles [hkl]* in the Funk transformation!
If a zone (great circle) already conotains a high number of poles, it is very likely that at intersection with other great circles not yet discovered bands exist. - Connect strong poles [hkl]* to define their zone axis and check new intersection with other great circles!
They are often not obvious since bands are sometimes too low intense for the naked eye. - Connect preferably [hkl]* with small bandwidths in Funk transformation to define low-indexed zone axes [uvw]!
Other [hkl]* along this (uvw)* are very likely low indexed as well.
Many of the so defined bands can have a too low intensity or only display a single band edge only. Such bands are meaningless, except they can be used to define other usable bands.
Finally a few further recommendations:
- Try to find as many as possible bands.
Each additional band which confirms your lattice solution reduces the danger of misinterpretation. - Prevent asymmetric bands.
Since not used they become only disturbing the more bands you discover. - Switch on the check box in the menu “Lattice solutions“.
Sometimes profiles accidentally look like reliable bands! You should be sceptic, if a bandwidth generates a reciprocal lattice point which changes the lattice solution. This can happen (e.g. in the case of hematite), but it can be also a fake band. Then it is time to check the 3D presentation.