$GUESS
$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
ECP 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 group,
and you MUST pay attention to NORB below.
- = 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.
All GUESS types except 'SKIP' permit reordering of the
orbitals, carry out an orthonormalization of the orbitals,
and generate the correct initial density matrix. The
initial density matrix cannot be generated for -CI- and
-MCSCF-, so property restarts for these wavefunctions will
require 'SKIP' which is an otherwise seldom used option.
Note that correct computation of a -GVB- density matrix
requires CICOEF in $SCF. Another possible use for 'SKIP'
is to speed up a EXETYP=CHECK job, or a RUNTYP=HESSIAN job
where the hessian is supplied.
- PRTMO
- = a flag to control printing of the initial guess.
(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.
Input to this array gives the new molecular
orbital order. For example, IORDER(3)=4,3 will
interchange orbitals 3 and 4, while leaving the
other MOs in the original order. This parameter
applies to all orbitals (alpha and beta) except
for -UHF-, where it only affects the alpha MOs.
(default is IORDER(i)=i )
- JORDER
- = Reordering instructions.
Same as IORDER, but for the beta MOs of -UHF-.
- 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)
- 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. (default=.FALSE.)
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