`ANGULAR`,*method,acca,crowd*
`LMIN`,
`LMAX`,

Specify the details of the angular quadrature scheme.
The default choice for *method* is `LEBEDEV` (ie. as in
A. D. Becke, J. Chem. Phys. 88 (1988) 2547)
which provides angular grids of octahedral symmetry.
The alternative choice for *method* is `LEGENDRE`
which gives Gauss-Legendre quadrature in and simple quadrature in
, as defined by C. W. Murray, N. C. Handy and G. J. Laming,
Mol. Phys. 78 (1993) 997.

Each type of grid specifies a family of which the various members are
characterized by a single quantum number ; spherical harmonics up
to degree are integrated exactly.
and
specify allowed ranges of
for H-Be, B-Ca, Sc-Ba, and La-
respectively.
The
are further moderated at run time so that for
any given atom they are not less than or twice the maximum
angular momentum of the basis set on the atom; this constraint can be
overridden by giving a negative value in `LMIN`, and in this
case just its absolute value will be used as the lower bound.
For the Lebedev grids,
if the value of is not one of the set implemented in
MOLPRO (3, 5, 7, 9, 11, 13, 15, 17, 19, 23, 29, 41, 47, 53),
then is increased to give the next largest angular grid available.
In general, different radial points will have different , and in the
absence of any moderation described below, will be taken from
.

*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
to zero, will switch off this feature.

acca is a target energy accuracy. It is used to reduce for a given radial point as far as possible below but not lower than . 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.

molpro@molpro.net 2018-11-19