SPACE_GROUP

 NAME
SPACE_GROUP – Generate a simulation box applying symmetry operations to an input asymmetric unit

 SYNOPSIS
SPACE_GROUP   OPEN  filename  group

 DESCRIPTION
Read the space group group parameters (nonequivalent molecules and corresponding interchange matrices and fractional translations) form the ASCII file filename. The file filename is a user database which may contain many entries corresponding to different space groups. The following is an example of an entry of this file:

Space Group Symmetry P 2_1          
     2
      1.00       .00       .00
       .00      1.00       .00
       .00       .00      1.00
       .00       .00       .00
     -1.00       .00       .00
       .00      1.00       .00
       .00       .00     -1.00
       .00       .50       .00
Space Group Symmetry P 2/c          
     4
      1.00       .00       .00
       .00      1.00       .00
       .00       .00      1.00
       .00       .00       .00
     -1.00       .00       .00
       .00     -1.00       .00
       .00       .00      0.00
       .50       .00       .50
     -1.00       .00       .00
       .00      1.00       .00
       .00       .00     -1.00
       .00       .50       .50
      1.00       .00       .00
       .00     -1.00       .00
       .00       .00     -1.00
       .50       .50       .00

The space group file is parsed by ORAC as usual by interpreting the composing tokens of each line string. The space group name is taken to begin after the third word Symmetry in the first line and may be composed of more than one word. The number of nonequivalent molecules nmol in the cell is read in the immediately following line. Then, for each molecule, four lines must be provide where the interchange matrix and the fractional translations are read in. No comment lines may be included. In the present example, for the first molecule the identity matrix and the zero translation are given from line 3-6, while in, e.g., the $P2_{1}$ group, for the second molecule a $C_{2y}$ (line 7-9) rotation and a 0.5 fractional translation (line 10) along the same axis are given. The coordinates of the asymmetric unit must be provided in input through the command READ_PDB. The command REPLICATE is used to generate a simulation box larger than the unitary cell. Note that the cell parameters of the simulation box are input to the command CRYSTAL.

 EXAMPLES
SPACE_GROUP sgroup.dat P 2_1
The symmetry transformations of the space group $P 2\_1$ are applied to the asymmetric unit in order to generate the coordinates of the other molecules contained in the unit cell.