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.