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Tutorials and Examples

LMGP suite for Windows by Jean Laugier and Bernard Bochu

(Laboratoire des Materiaux et du Génie Physique de l'Ecole Supérieure de Physique de Grenoble http://www.inpg.fr/LMGP/)

Basic Demonstration of OrientExpress for orienting a single crystal from a single Laue Photograph

The CCP14 Homepage is at http://www.ccp14.ac.uk

[Tutorials page] | [LMGP Suite Index]

OrientExpress is obtained as a Windows executable from the LMGP (Laboratoire des Materiaux et du Génie Physique de l'Ecole Supérieure de Physique de Grenoble http://www.inpg.fr/LMGP/) suite program area at http://www.ccp14.ac.uk/ccp/web-mirrors/lmgp-laugier-bochu/.

OrientExpress is used to orient a single crystal of known unit cell dimensions from a single Laue Photograph.

Running OrientExpress brings up the following starting Screen.

  • Initial OrientExpress Screen

  • 7th May 2001 updates to OrientExpress that have not made it into an updated tutorial

    1. The use of scanner images:
      • The previous version caused some problems with JPEG format images. The new version creates a bitmap fileon the disk from the JPEG file and wortks wth it.
      • The coordinates measurement on an image: The zoom image is permanent besides the image and the user can use it to estimate the center of a spot.
      • The determination of the beam centre with a circle (back scattering case) was improved.
    2. The data modifications can be made directly on the panel "Data". This is interesting to find the good crystal-detector distance whixh is often ill known and also to show the effect of some parameters on the simulation (distance, wavelength range, space group, etc...).
    3. The indexation search: In the previous version the user could type the estimated Miller indices of two reflections. Now these indices are interpreted as indices of a form of planes {hkl, no longer like (hkl). For example, with a cubic crystal if the user believe that the first spot corresponds to a 4-fold axis and the second one to a 2-axis, he can give 001 and 110 (angle = 90) or 001 and 101 (angle=45). The program will search the good indices.

    Selecting via the menu, the Data, Keyboard option will give you the following dialog box to enter the data on your sample, (Cell, system, lattice type).

  • Initial Data Entry

  • This data can also be retrieved from a past file by using the Data, File menu and selecting a *.dat file containing the relevant data.

  • Opening an old data file in OrientExpress

  • Using the Coordinates menu, you can open a set of co-ordinates previously obtained from a Laue image (for immediate indexing); or open up a Laue BMP image file to obtain the coodinates. In this case, we will open up a Laue BMP or JPG image file using the Coordinates, Image menu command.

  • Opening a Laue BMP Image file

  • OrientExpress has menu options under the Origin, and Scale menu options for centering and scaling the image. The choosen spots must have Miller indices as small as possible (often lying at the crossing of zonal lines). After centering and scaling, select the Measure coord menu option and start clicking on some spots by clicking on them with the mouse. When you click on a spot, a zoom window will come up so you can easily click on the centre of the spot.

  • Selecting Laue Spots with the Mouse
  • Selecting Laue Spots with the Mouse

  • When you have selected enough spots (4 to 6 is the best begining) save the coordinates using the Save coord menu option leaving you with the following screen.

  • Have coordinates from the Laue image

  • Select Indexing search from the menu which will bring up the following options box.

  • Options box for indexing search.

  • Accept the defaults or put in your own parameter and then click OK to start the indexing.

    After OrientExpress obtains a result (if not try again), this will be simulated on top of the image (if you used an image to derive the spots: you can load an image at a later date if you used a coordinate file).

  • OrientExpress

  • After indexing, OrientExpress then gives further options for simulation and re-orientation that you can explore. This includes calculation of angles to reorient the crystal.

  • Calculation of Angles to reorient the crystal

  • [Tutorials page] | [LMGP Suite Index]

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