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
EUHEDRAL is not a stand-alone program, but uses the
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
Also available is a
tar file with test data
(ECM 21 Durban Workshop on 24 august 2003).
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
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
The definition of the used coordinate systems can be found
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.
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
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
The routine filter determines
equivalent reflections based on the
point group symmetry of the crystal.
The refinement strategy depends on the information which is available from the
Crystal dimensions known, crystal faces
indexed: Strategy 1
Crystal dimensions known, crystal faces not indexed:
No previous information: Strategy 3
After the initial refinements a reasonable starting model should have been
obtained. This can now be fine-tuned.
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
ABST or ABSG ?
- version 1.4 (10 july 2006)
- onerot and partialrot are now hardware independent.
(viewspeed default set to 30 degrees/second)
- after volume refinement, reset window scale.
- fortran-77 intrinsics DATE and SYSTEM avoided
- ported to gfortran-4.1
- version 1.3 (12 january 2004)
- Bug fix: buildcube in GUI now works.
- version 1.2 (7 august 2003)
- version 1.1 (6 may 2002)
- In the calculation of Rpsi
the value of intmin is set to at least 0.01 to prevent a division by zero.
- version 1.0 (19 nov 2001)
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.
Postal address: Laboratory for Crystal and Structural Chemistry,
Bijvoet Center for Biomolecular Research, Padualaan 8,
NL-3584 CH Utrecht, The Netherlands.
EUHEDRAL version 1.4 (10 Jul 2006)