7.9. Phase combination
Keyword: phase combination, SIGMA_A, CCP4 interface, MTZ

MAIN does not include its own phase combination procedure.  Herein a
link to CCP4 SIGMAA program (written by R. Read) is described (use
"PHASE_CMB" on page 10 "MAIN_CMDS:phase_comb.cmds").  Parts of the
macro can be used also to exchange structure factor information
between MAIN and CCP4 .

The FCALC are written to a file for further processing with CCP4
programs.  The spawn command starts a shell script
"MAIN:doc/dens_mod/phase_comb/main_2_sigmaa_2_main.ccp4" and preforms
the phase combination.  The example file is in the
"MAIN:doc/dens_mod/phase_comb/" directory.

> write over file main_fcalc.phase refl polar select defined end
> spawn main_2_sigmaa_2_main.ccp4  > sigmma.out
> read file sigmaa.phase refl over resol RESOL_MIN RESOL_MAX friedel

The retrieved phases are stored in FOBS, so click the "FOBS_MAP" item
and calling "MAIN_CMDS:calc_fo_map.cmds" macro to calculate the new
map.