Coordinate systems in FACELIFT

FACELIFT 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 FACELIFT 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 the RMAT file is supplied by the user (filename: name.rmat corresponding to name.ins), FACELIFT will use it. If the file is not supplied an arbitrary rmat will be generated by FACELIFT. The supplied RMAT file is checked by FACELIFT for consistancy with the supplied cell parameters in name.ins.

In many FACELIFT routines the user can make use of the cartesian coordinate system. In this context x y z is used.