MOLPRO

17 THE DENSITY FUNCTIONAL PROGRAM 113
the next largest angular grid available. In general, different radial points will have different l,
and in the absence of any moderation described below, will be taken from l max
i .
crowd is a parameter to control the reduction of the degree of quadrature close to the nucleus,
where points would otherwise be unnecessarily close together; larger values of crowd mean less
reduction thus larger grids. A very large value of this parameter, or, conventionally, setting it
c;to zero, will switch off this feature.
acca is a target energy accuracy. It is used to reduce l for a given radial point as far as possible
below li
max but not lower than li
max . The implementation uses the error in the angular integral of
the kernel of the Slater-Dirac exchange functional using a sum of approximate atomic densities.
If acca is zero, the global threshold is used instead, or else it is ignored.
17.3.4 Atom partitioning of integration grid (VORONOI)
VORONOI,m µ
Controls Becke-Voronoi partitioning of space. The algorithm of C. W. Murray, N. C. Handy and
G. J. Laming, Mol. Phys. 78 (1993) 997 is used, with m µ defined by equation (24). The default
value is 10.
17.3.5 Grid caching (GRIDSAVE, NOGRIDSAVE)
NOGRIDSAVE
disables the disk caching of the grid, i.e, forces the recalculation of the grid each time it is
needed.
GRIDSAVE
forces the use of a grid cache where possible.
17.3.6 Grid symmetry (GRIDSYM,NOGRIDSYM)
NOGRIDSYM
switches off the use of symmetry in generating the integration grid, whereas
GRIDSYM
forces the use of any point-group symmetry.
17.3.7 Grid printing (GRIDPRINT)
GRIDPRINT,key=value,...
controls printing of the grid, which by default is not done. At present, the only possible value
for key is GRID, and value should be specified as an integer. GRID=0 causes the total number
of integration points to be evaluated and reported; GRID=1 additionally shows the number of
points on each atom; GRID=2 causes the complete set of grid points and weights to be printed.