----- header of xpowder.pro extracted on: Fri May 31 15:31:06 2013 ----- Documentation for /scisoft/xop2.3/src_idl/dabax/xpowder.pro ----- XPOWDER: X-ray diffraction patterns for powder samples This application calculates a X-ray diffraction pattern for a powder crystal. The application is divided in three panels: "Asym Unit", "Unit Cell" and "Reflections" The main application is under the third panel "Reflection". The first two panels are optional with tools to help the user to load and eventually compute the unit cell. The calculation of the powder pattern is done in the routine xpowder_calchkl(), which basically i) loads the information of the unit cell (either fom the "Unit Cell" panel or from a file *.ucell, being this a text ASCII file containing in the first line a b c alpha beta gamma (in Angstroms the lengths, and in deg the angles) and then a number of lines, one per atom in the unit cell, with Z, occupation number, x, y and z (coordinates in crystal units). example: Silicon.ucell: 5.43070 5.43070 5.43070 90.0000 90.0000 90.0000 14 1.0 0.0 0.0 0.0 14 1.0 0.0 0.5 0.5 14 1.0 0.5 0.0 0.5 14 1.0 0.5 0.5 0.0 14 1.0 .25 .25 .25 14 1.0 .25 .75 .75 14 1.0 .75 .25 .75 14 1.0 .75 .75 .25 ii) Calculate all possible reflections (permutations of h k l indices) iii) Computes the Structure Factor for each reflection, and the intensity (only unpolarized beams are used by now). Reflections with intensity inder a cutoff value (in %) are eliminated (considered forbidden reflections). iv) Classifies and displays results. The Panel "Unit Cell" permits to load a unit cell, either from a *.ucell file or from the DABAX database. The Panel "Asym Unit" contains tools to compute the unit cell. For that, the user must enter the atoms in the Asymmetric Unit, and the symmetry operations to be applied. When the "Compute Atoms in the Unit Cell" button is pressed, the calculation is performed in the following way: every atoms in the asym. unit is transformed using all the symmetry operations. The redundant atoms are eliminated (and counted for calculating their multiplicity). Optionally, the operations of the 230 spatial symmetry groups can be load from the SpatialGroups.dat DABAX file. Note that this file contains the 230 groups and their names as obtained from: http://www.cryst.ehu.es/ (GENPOS application) All the application information can be stored in a xpowder input file for being restored lately. In addition, the user can create text files with information that can be loaded in the table widgets, by tagging the inputs in the following way: For Entering data in the "Asym Unit" panel, tag the inputs in this way (example): AUATOMS 57 0.9840 0.0 0.0 0.0 La 5 1.0 .19930 .5 .5 B AUATOMS AUSYM x,y,z -x,-y,z -x,y,-z AUSYM This file can be reaf using File->Load xpowder input file... In the same way, information in the "Unit Cell" panel are tagged as: UCATOMS 57.00 0.9840 0.000 0.000 0.000 La 5.000 1.000 0.1993 0.5000 0.5000 B 5.000 1.000 0.8007 0.5000 0.5000 B 5.000 1.000 0.5000 0.1993 0.5000 B 5.000 1.000 0.5000 0.8007 0.5000 B 5.000 1.000 0.5000 0.5000 0.1993 B 5.000 1.000 0.5000 0.5000 0.8007 B UCATOMS UCCELL 4.15271 4.15271 4.15271 90.0000 90.0000 90.0000 UCCELL Author: Manuel Sanchez del Rio, March 2007 Modification history: 2007-05-16 srio@esrf.fr added INFO tag,reference directory COPYRIGHT: XPOWDER belongs to XOP package and it is distributed within XOP. PLEASE REFER TO THE XOP COPYRIGHT NOTICE REFERENCE: Published calculations made with XOP should refer: M. Sanchez del Rio and R. J. Dejus "Status of XOP: an x-ray optics software toolkit" SPIE Proceedings Vol. 5536 (2004) pp.171-174 http://dx.doi.org/10.1117/12.560903 LAST MODIFICATION: srio@esrf.eu 2008-02-01