### Q.897 - How can I feed O-style symm-ops into Gerard's programs ?

Category: S.897 - general

Several programs require input of a set of spacegroup symmetry operators in O format. To make this easier, you can now define an environment variable OSYM which should point to your local directory that contains the collection of spacegroup operator files (usually, $ODAT/symm). In Uppsala, put the following in your .cshrc file:  setenv OSYM /nfs/taj/alwyn/o/data/symm/  When asked for a file with spacegroup operators in O format, you may either provide a filename, or the name of a spacegroup (including blanks if you like; case doesn't matter). The program will try to open the following files, assuming that STRING is the name you provided: 1. open a file called STRING 2. if this fails, check if OSYM is defined and open$OSYM/STRING
3. if this fails, open $OSYM/string.sym 4. if this fails, open$OSYM/string.o

For instance, if you type "p61.sym", the program will first try to open this file in your current directory. If that fails, it will look for it in the $OSYM directory. Similarly, typing "P 43 21 2" should result in the program finding the file$OSYM/p43212.sym.

Hint: if you make soft links in the OSYM directory, you can also type spacegroup numbers (e.g.: \ln -s p212121.sym 19). See OMAC news below. Theoretically, this should also allow you to type "19" in the Symm_setup command in O, but I haven't tested this yet.

Hint: use Phil Evans' program gen_o_symm.f (file://rose.bmc.uu.se/pub/gerard/omac/gen_o_symm.f) to generate the complete set of spacegroup operator files from the CCP4 symop.lib file.