The unit cell data file contains 3 initial lines and one line per atom in the unit cell. All lines are in free format, beginning in the left most column.
Line 1: Title up to 80 characters line 2: Space group symbol [,origin choice number] line 3: Lattice constants a,b,c,alpha,beta,gamma
and for each atom a line with:
Name(4 characters) x y z isotropic B
Empty lines be in the cell data file will be ignored.
Example
Single atom structure of NA Pm-3m 5.0 5.0 5.0 90. 90. 90. NA1+ 0.0 0.0 0.0 0.1
The title can be any character string up to 80 characters long
The space group symbol is used to generate all atoms within the unit cell. The symbols used should be the Hermann-Mauguin symbols used in Int. Tables Vol.A. A center of inversion should be given as "-" sign immediately preceeding the axis. Lattice types need to be given as capital characters, mirror planes as small characters.
Monoclinic cell choices 2,3 or unique c-axis will be assumed if the corresponding non standard Hermann-Mauguin symbol is used.
Origin choice 2 is indicated by setting the optional second parameter to "2".
The lattice constants are used to distinguish between rhombohedral and hexagonal settings.
The space group symbol is checked for contradictions with the lattice constants. In case of error, the unit cell is not read.
The lattice constants are read in free format <a b c alpha beta gamma> All six constants must be given.
The space group symbol is checked for contradictions with the lattice constants. In case of error, the unit cell is not read.
If a unit cell is read, only those atoms in the asymmetric unit should be listed. For each of the atoms a line must be given with the name of the atom, the fractional coordinates and the isotropic thermal coefficient B. The name (in capital characters) must be leftbound in the first four columns, the numerical values can be in free format. Optionally charged atomes can be symbolised by e.g. "NA1+". See the help entry 'atom names' for a complete list of atoms for which scattering curves are supplied.
Empty lines in the file are ignored.