Project 6: Java Lauegrams for Quasicrystals

Steffen Weber, July 1997, (update 10/24/01)


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I am in the process of updating this applet ..., so this is a beta version


This applet simulates X-ray Diffraction patterns for the Laue method (transmission/backreflection mode). NOTE on the quasicrystal systems:
-you may select among the octagonal (8fold), decagonal (10fold), dodecagonal (12fold) and icosahedral systems
-the capital letters 'S:' and 'Y:' indicate the usage of STEURER's or YAMAMOTO's lattice matrices 

Film size and Film distance
The Film size is set as 120 x 120 mm. The film-sample-distance (FSD) is set as 50 mm. Therefore in transmission mode reflections with theta<=25 deg and in backreflection mode reflections with theta>=65 deg are plotted.

NOTE on STEURER and YAMAMOTO matrices:
- the two leading authorities on numerical structure analysis of quasicrystals are Dr.Akiji Yamamoto and Prof.Walter Steurer
- they use different lattice matrices 
- their lattice constants 'a' are not the same

NOTE on the OCTAGONAL, DECAGONAL, DODECAGONAL system:
- do use 5 integers for the orientation vector (separate components by SPACE)
- give 'a' & 'c' as lattice constant

NOTE on the ICOSAHEDRAL system:
- do use 6 integers for the orientation vector (separate components by SPACE)
- give 'a' as lattice constant

NOTE on the maximum order:
-due to the loop over 5 or 6 integer indices the number of generated poles might be high. I reseved arrays for upto 10.000 poles. The calculation might be very time consuming though. Therefore I recommend not to exceed max.oder=1 (icosahedral system) or max.order=2 (for the other systems).

NOTE on the indices:
- just click the poles to get their indices.


NOTE on max. qi:
You may limit the number of generated reflections by setting smaller values for the internal space component of the diffraction vector q. This is reasonable since reflections with large internal space components are weak and often not observable. NOTE on spot radii:
You may select fixed spotsizes or use a rough approximation for the intensities, which is Intensity is proportional to the inverse of the internal space component of the diffraction vector. [spot radii ~1/qi]