Set or overwrite box information for frames.

box {[x <xval>] 
     [y <yval>] 
     [z <zval>] {[alpha <a>][beta <b>][gamma <g>][truncoct]} | nobox | auto [offset <offset> | 
                 getbox {ucell|frac|shape} [name <setname>] [out <file>] ] 
                 [radii {vdw | gb | parse | none }]

[x <xval>] [y <yval>] [z <zval>] Change box length(s) to specified value(s).
[alpha <a>] [beta <b>] [gamma <g>] Change box angle(s) to specified value(s).
[truncoct] Set box angles to truncated octahedron.
[nobox] Remove any existing box information.
auto Set an orthogonal bounding box enclosing all atoms by the specified radii and an optional offset.
offset <offset> Offset in Angstroms to add to each box length (both + and -).
getbox Save existing box information to a 3×3 matrix data set.
radii {vdw | gb | parse | none} Radii to use for each atom: van der Waals, generalized Born, PARSE, or no radii.

Modify box information during trajectory processing. Note that this will permanently modify the box information for topology files during trajectory processing as well. It is possible to modify any number of the box parameters (e.g. only the Z length can be modified if desired while leaving all other parameters intact).

If no box is present, an orthogonal bounding box enclosing all atoms can be created with the auto keyword. If getbox is specified, the existing box information will be saved to a data set.