EMLaue

Laue Pattern Simulation

While the EMLauemaster program produces a master pattern, similar to the EMEBSDmaster program, the EMLaue program can be used to compute individual transmission and reflection Laue patterns for a given detector geometry and an arbitrary crystal structure.

Using the standard command line approach, the template file can be obtained; this file contains the following parameters:

 &LaueData
! The line above must not be changed
!
! The values below are the default values for this program
!
! crystal structure file name
 xtalname = 'undefined',
! detector x-size (pixels)
 numpx = 1024,
! detector y-size (pixels)
 numpy = 768,
! number of parallel threads
 nthreads = 1,
! detector pixel size (microns, square pixels)
 pixelsize = 50.0,
! spot size weight factor (basically 1/(2*sigma^2) for Gaussian peaks)
 spotw = 0.1,
! intensity scaling gamma factor
 gammavalue = 1.0,
! x-ray tube accelerating voltage (kV)
 maxVoltage = 30.0,
! cutoff lower voltage (kV)
 minVoltage = 15.0,
! sample-detector distance (mm)
 SDdistance = 100.0,
! do we need to store backprojections as well ?  'Yes' or 'No'
 backprojection = 'No',
! dimension of square Lambert array for backprojection (actual will be 2*BPx+1 by 2*BPx+1)
 BPx = 300,
! laue pattern mode 'transmission' or 'reflection'
 Lauemode = 'transmission',
! input file with list of orientations
 orientationfile = 'undefined'
! prefix for tiff output files with individual patterns
 tiffprefix = 'undefined',
! HDF output file name (relative to EMdatapathname)
 hdfname = 'undefined',
 /

Most of the parameters are easily interpreted. The forward model employs a simple Gaussian for the intensity profile of individual pattern spots. The backprojected Laue patterns can also be stored on a square Lambert grid; this is sometimes useful for testing purposes in the context of spherical indexing. The examples below show the input files for transmission and reflection Laue patterns for the standard [10.0] zone axis orientation of trigonal calcite, using an x-ray tube voltage of 30 kV and a low energy cutoff at 15 kV

 xtalname = 'Calcite.xtal',
 numpx = 512,
 numpy = 512,
 nthreads = 1,
 pixelsize = 100.0,
 spotw = 0.5,
 gammavalue = 0.33333,
 maxVoltage = 30.0,
 minVoltage = 15.0,
 SDdistance = 12.5,
 backprojection = 'No',
 Lauemode = 'reflection',
 orientationfile = 'path/eulers.txt'
 tiffprefix = 'path/Calcite-reflection_',
 hdfname = 'path/Calcite-reflection.h5',
 /

The eulers.txt file has the following content:

eu
     1
      0.000000      0.000000      0.000000