$SODET group                 (required if CITYP=FSOCI)
 
    This group controls a full second order CI calculation
using determinants (see also the keyword SOCI in $CIDRT).
Most of the characteristics of the active space (such as
NCORE, NACT, NELS) must be given by $CIDET input, as a
preliminary full CI according to $CIDET will be made.  The
FCI states will then used as the initial guess for the full
second order CI.  A few additional parameters may be given
in this group, but many runs will not need to give any of
these.
 
NEXT   = the number of external orbitals to be included.
         The default is the entire virtual MO space.
 
NSOST  = the number of states to be found in the SOCI.
         The default is copied from NSTATE in $CIDET.
 
MAXPSO = maximum expansion space size used in the SOCI.
         The default is copied from MXXPAN in $CIDET.
 
ORBS   = MOS means use the MCSCF orbitals, which should be
             allowed to undergo canonicalization (see the
             CANONC keyword in $MCSCF), or the input $VEC
             group in case SCFTYP=NONE. (default)
         NOS means to instead use the natural orbitals of
             the MCSCF.