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In X-ray crystallography the analytical absorption correction based on an accurate crystal description is still the best absorption correction method. Unfortunately it can be difficult to measure the crystal size and to index the crystal faces. Several laboratories have therefore developed computer programs to refine the initial crystal description (e.g. the HABITUS program of W. Herrendorf). Our program EUHEDRAL was developed for the refinement of the crystal shape against the intensities of multiple measured reflections coming from redundant area detector data. The program was developed to provide the highest possible flexibility (refinement of crystal volume and face distances, rotation of the crystal with respect to the crystal axes, and tilting of individual faces). It is the decission of the program user, which methods should be applied for the individual crystal.

The refinement cycles of EUHEDRAL usually need a lot of computer power and computer time. We nevertheless think that the obtained results are promising. Of cource, EUHEDRAL should only be used, when an analytical absorption correction makes sense (absorption coefficient larger than about 2 mm-1).

EUHEDRAL is not a stand-alone program, but uses the PLATON package for absorption correction. Please be aware, that PLATON is updated regularly and that you should use a recent version. Please install PLATON in the searchpath of your computer.

Download and Installation

Download and installation instructions for EUHEDRAL can be found here.
Also available is a tar file with test data (ECM 21 Durban Workshop on 24 august 2003).

Input files

The program EUHEDRAL needs two input files:
The names and the extensions of the files can be chosen by the user. It is advisable to create a separate working directory containing these files for each EUHEDRAL project and to start the program within this directory.


By typing help at the EUHEDRAL prompt, netscape is started to display this documentation.

By typing a question mark ? at the prompt, you obtain a list of available commands.

Coordinate systems

The definition of the used coordinate systems can be found here.


All EUHEDRAL refinements of the crystal shape are based on a merging R-value R2 which can be defined by the user via the weight command.

First step

After starting the program EUHEDRAL, the command filter should be called. filter reduces the initial data to a smaller subfile, which is then used for the refinement. Several filterparameters can be chosen. The size of the subfile determines the speed and the reliability of the refinement:
small → higher speed
large → higher reliability

With the graphical display of filter, the user can check whether the whole surface of the crystal is covered by the chosen subfile. The positions of the incoming and the outgoing beam of the filtered reflections are displayed.

The routine filter determines equivalent reflections based on the point group symmetry of the crystal.

Initial refinements

sphere The refinement strategy depends on the information which is available from the start:

Crystal dimensions known, crystal faces indexed: Strategy 1
Crystal dimensions known, crystal faces not indexed: Strategy 2
No previous information: Strategy 3

Final refinements

After the initial refinements a reasonable starting model should have been obtained. This can now be fine-tuned. Suggestions.

Performing absorption correction

The refined file name.ins can directly be used as an input file for PLATON to perform an absorption correction on the complete reflection file name.hkl

Useful hints

Known bugs

Version history

Final Notes

Disclaimer: you use EUHEDRAL freely, but at your own responsibility completely.

Please do report failures, give comments and ask questions, preferable via e-mail, we will help you as much as possible.
Email: m.lutz or a.m.m.schreurs.
Postal address: Laboratory for Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Padualaan 8, NL-3584 CH Utrecht, The Netherlands.
EUHEDRAL version 1.6 (15 september 2008)