Coordinate systems in EUHEDRAL
EUHEDRAL was developed in close relation to the program PLATON.
For absorption correction PLATON makes use of the direction cosines
as defined in SHELX-76. These direction cosines are defined with
respect to the coordinate system of the crystal (reciprocal axes).
Therefore they are independent of the used diffractometer.
In many EUHEDRAL routines the user can make use of the crystal
coordinate system. In this context h k l refers
to the reciprocal axes of the crystal coordinate system.
We have defined a cartesian coordinate system (diffractometer or laboratory
coordinate system): origin on the crystal,
X-axis points to Xray source, Z-axis points to zenith, and the Y-axis
completes the right-handed system.
The crystal coordinate system is transformed into the cartesian
system with the RMAT orientation matrix.
If an rmatfile file is supplied by the user
(filename: name.rmat corresponding to name.ins), EUHEDRAL will use it.
If the file is not supplied an arbitrary rmat will be generated by EUHEDRAL.
The supplied RMAT file is checked by EUHEDRAL for
consistancy with the supplied cell parameters in
name.ins.
In many EUHEDRAL routines the user can make use of the cartesian
coordinate system. In this context x y z
is used.