Prerequisites

1.
 Both aoforce and even
more Numforce require well converged SCF/DFTcalculations (e.g. $scfconv 8 and
jobex [ri] gcart 4).

2.
 The maximum core memory the program aoforce is allowed to allocate should be
defined in the data group $maxcor; the recommended value is about 50% of the
available (physical) core memory (in case of RIcalculations subtract the memory
specified in $ricore).

3.
 To start aoforce in the lowest eigenvalue search mode, use the keyword $les. For its
use as well as other keywords dealing with the calculation of only some irreps, see the
Referenceguide part of this manual.

4.
 Numforce additionally requires the file gradient and will not work, if the calculation
is not done at a stationary point of the molecular total energy. For reliable results,
always use Numforce with the option central (i.e. central differences) and be aware
of effects due to the step length (option d real;, default value is 0.02 a.u.). It is
strongly recommended to use Numforce in DFT calculations only with the option
weight derivatives in $dft, since this provides more accurate gradients and thus
frequencies, see Section 21.2.10.

5.
 The Numforce script can be run for different levels of theory, which means that the
binaries it calls have to be specified additionally. To perform calculations using the
RI approximation, call Numforce with the option ri. MP2 and CC2 calculations are
requested via the options level mp2 and level cc2, respectively. NumForce works
also on the RIRPA level with level rirpa (note: the ri option must be used in
this case). To select the correct option(s), use the explanations you get by calling
NumForce h.
For a review of theory and implementation see refs. [158,159].