Grid

The Grid key is available either as simple key, or as block key.

The simple key options are as follows:

GRID {save} {coarse|medium|fine}

If the word save is specified, the program will store all grid points on TAPE41 (in addition to the specification of the grid that is always stored). The default is NOT to store all grid points.

Either coarse, medium or fine may be specified. This instructs the program to generate the grid automatically within a box enclosing all atoms of the molecule. The distance between grid points is 0.5, 0.2 or 0.1 bohr for respectively a coarse, medium or fine grid. Evidently the size of the result file TAPE41 depends strongly on this specification. The default value (used when the user does not specify the grid) is to generate a coarse grid.

If GRID is used as a block key it must be followed by the word end in a later record. The records until the end are the data for the Grid keyword:

Grid {save}
 x0, y0, z0
 n1, n2, n3
 v1x, v1y, v1z, length1
 v2x, v2y, v2z, length2
 v3x, v3y, v3z, length3
END

If the word save is specified, the program will store all grid points on TAPE41 (in addition to the specification of the grid that is always stored). The default is NOT to store all grid points.

The records in the data block must contain (in the order specified below!):

• 1 Three coordinates for the 'origin' (lower-left corner) of the grid.
• 2 Three integers: the numbers of points in three independent directions.
  If fewer integers are supplied the grid will accordingly be less-dimensional.
• 3 Three records each containing the coordinates for the direction of the independent vector (size irrelevant)
  and the total length of the grid in that direction.
  If a lower-dimensional grid is requested (see item #2), then fewer such direction-records are read and
  the redundant ones, if any, are ignored.
  The unit of length in which the grid size is input is by default Angstrom.
  The default can be overridden by using the input key UNITS, see below.

Notes:

• The second record ('three integers...') specifies the number of grid points in the different directions.
  The corresponding number of steps or intervals is one less!
• If the TAPE41 result file is to be used by the contour generating program cntrs,
  the grid used in the densf calculation must be two-dimensional.
• If the TAPE41 result file is to be used by ADFview, the grid used must be an three-dimensional orthogonal grid,
  with a single step size for all three dimensions.
• If the output TAPE41 file already exists and it contains valid grid data or if CUBINPUT is specified then the GRID input is ignored.
• The unit of length used in the input file has no relation to how the data are stored on the result file
  and how the program processes the data internally.
  Internal processing and storage on file is in bohr (atomic units).