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$GUESS group (optional, relevant for all SCFTYP's)
This group controls the selection of initial molecular
orbitals.
GUESS = Selects type of initial orbital guess.
= HUCKEL Carry out an extended Huckel calculation
using a Huzinaga MINI basis set, and
project this onto the current basis.
This is implemented for atoms up to Rn,
and will work for any all electron or
core potential basis set.
(default for most runs)
= HCORE Diagonalize the one electron Hamiltonian
to obtain the initial guess orbitals.
This method is applicable to any basis
set, but does not work as well as the
HUCKEL guess.
= MOREAD Read in formatted vectors punched by an
earlier run. This requires a $VEC deck,
and you MUST pay attention to NORB below.
= RDMINI Read in a $VEC deck from a converged SCF
calculation using GBASIS=MINI, to project
the MINI orbitals onto the current basis.
The option improves upon the Huckel guess
because it involves SCF orbitals, which
are typically easily obtained in the small
MINI basis. This option doesn't work if
the current basis uses core potentials.
potentials. The $VEC from the MINI run
must contain all virtual orbitals.
= MOSAVED (default for restarts) The initial
orbitals are read from the DICTNRY file
of the earlier run.
= SKIP Bypass initial orbital selection. The
initial orbitals and density matrix are
assumed to be in the DICTNRY file. Mostly
used for RUNTYP=HESSIAN when the hessian
is being read in from the input.
The next options are less general, being for Fragment
Molecular Orbital runs, or Divide and Conquer runs:
= FMO Read orbitals from the DICTNRY file, from
previous FMO run with MODPRP=1.
= HUCSUB Perform a Huckel guess in each subsystem
of a Divide and Conquer run
= DMREAD Read a density matrix from a formatted $DM
group, produced by a previous Divide and
Conquer run, see NDCPRT in $DANDC.
All GUESS types except 'SKIP' permit reordering of the
orbitals, carry out an orthonormalization of the orbitals,
and generate the correct initial density matrix, for RHF,
UHF, ROHF, and GVB, but note that correct computation of
the GVB density requires also CICOEF in $SCF. The density
matrix cannot be generated from the orbitals alone for MP2,
CI, or MCSCF, so property evaluation for these should be
RUNTYP=ENERGY rather than RUNTYP=PROP using GUESS=MOREAD.
PRTMO = a flag to control printing of the initial guess.
(default=.FALSE.)
PUNMO = a flag to control punching of the initial guess.
(default=.FALSE.)
MIX = rotate the alpha and beta HOMO and LUMO orbitals
so as to generate inequivalent alpha and beta
orbital spaces. This pertains to UHF singlets
only. This may require use of NOSYM=1 in $CONTRL
depending on your situation. (default=.FALSE.)
NORB = The number of orbitals to be read in the $VEC
group. This applies only to GUESS=MOREAD.
For -RHF-, -UHF-, -ROHF-, and -GVB-, NORB defaults to the
number of occupied orbitals. NORB must be given for -CI-
and -MCSCF-. For -UHF-, if NORB is not given, only the
occupied alpha and beta orbitals should be given, back to
back. Otherwise, both alpha and beta orbitals must
consist of NORB vectors.
NORB may be larger than the number of occupied MOs, if you
wish to read in the virtual orbitals. If NORB is less
than the number of atomic orbitals, the remaining orbitals
are generated as the orthogonal complement to those read.
NORDER = Orbital reordering switch.
= 0 No reordering (default)
= 1 Reorder according to IORDER and JORDER.
IORDER = Reordering instructions, giving the new molecular
orbital order. This parameter applies to the
common orbitals (both alpha and beta) except for
UHF, where IORDER only affects the alpha MOs.
Examples (let there be 10 occupied orbitals):
transposition of HOMO and LUMO:
IORDER(10)=11,10
a different transposition:
IORDER(10)=15 IORDER(15)=10
a more general permutation:
IORDER(8)=11,8,9,10
so the new orbital 10 is the original 9th.
The default is IORDER(i)=i.
JORDER = Reordering instructions.
Same as IORDER, but for the beta MOs of UHF.
INSORB = the first INSORB orbitals specified in the $VEC
group will be inserted into the Huckel guess,
making the guess a hybrid of HUCKEL/MOREAD. This
keyword is meaningful only when GUESS=HUCKEL, and
it is useful mainly for QM/MM runs where some
orbitals (buffer) are frozen and need to be
transferred to the initial guess vector set,
see $MOFRZ. (default=0)
* * * the next are 3 ways to clean up orbitals * * *
PURIFY = flag to symmetrize starting orbitals. This is the
most soundly based of the possible procedures.
However it may fail in complicated groups when the
orbitals are very unsymmetric. (default=.FALSE.)
TOLZ = level below which MO coefficients will be set
to zero. (default=1.0E-7)
TOLE = level at which MO coefficients will be equated.
This is a relative level, coefficients are set
equal if one agrees in magnitude to TOLE times
the other. (default=5.0E-5)
SYMDEN = project the initial density in order to generate
symmetric orbitals. This may be useful if the
HUCKEL or HCORE guess types give orbitals of
impure symmetry (?'s present). The procedure
will generate a fairly high starting energy, and
thus its use may not be a good idea for orbitals
of the quality of MOREAD. (default=.FALSE.)
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generated on 7/7/2017