the information below taken from the Firefly manual:
$FFCALC group (relevant for RUNTYP=FFIELD)
This group permits the study of the influence of an
applied electric field on the wavefunction. The most
common finite field calculation applies a sequence of
fields to extract the linear polarizability and first and
second order hyperpolarizability. The method is general,
and so works for all ab initio wavefunctions in Firefly.
EFIELD = applied electric field strength
IAXIS and JAXIS specify the orientation of the applied
field. 1,2,3 mean x,y,z respectively.
The default is IAXIS=3 and JAXIS=0.
If IAXIS=i and JAXIS=0, the program computes alpha(ii),
beta(iii), and gamma(iiii) from the energy changes, and
a few more components from the dipole changes. Five
wavefunction evaluations are performed.
If IAXIS=i and JAXIS=j, the program computes the cross
terms beta(ijj), beta(iij), and gamma(iijj) from the
energy changes, and a few more components from the
dipole changes. This requires nine evaluations of the
AOFF = a flag to permit evaluation of alpha(ij)
when the dipole moment is not available.
This is necessary only for MP2, and means
the off-axial calculation will do 13, not
9 energy evaluations. Default=.FALSE.
SYM = a flag to specify when the fields to be
applied along the IAXIS and/or JAXIS (or
according to EONE below) do not break the
molecular symmetry. Since most fields do
break symmetry, the default is .FALSE.
ONEFLD = a flag to specify a single applied field
calculation will be performed. Only the
energy and dipole moment under this field
are computed. If this option is selected,
only SYM and EONE input is heeded. The
default is .FALSE.
EONE = an array of the three x,y,z components of
the single applied field.
Finite field calculations require large basis sets,
and extraordinary accuracy in the wavefunction. To
converge the SCF to many digits is sometimes problematic,
but we suggest you use the input to increase integral
accuracy and wavefunction convergence, for example
$CONTRL ICUT=20 ITOL=30 INTTYP=HONDO $END
$SCF NCONV=10 FDIFF=.FALSE. $END
In many cases, the applied fields will destroy the
molecular symmetry. This means the integrals are
calculated once with point group symmetry to do the
initial field free wavefunction evaluation, and then again
with point group symmetry turned off. If the fields
applied do not destroy symmetry, you can avoid this second
calculation of the integrals by SYM=.TRUE. This option
also permits use of symmetry during the applied field
Examples of fields that do not break symmetry are a
Z-axis field for an axial point group which is not
centrosymmetric (i.e. C2v). However, a second field in
the X or Y direction does break the C2v symmetry.
Application of a Z-axis field for benzene breaks D6h
symmetry. However, you could enter the group as C6v in
$DATA while using D6h coordinates, and regain the prospect
of using SYM=.TRUE. If you wanted to go on to apply a
second field for benzene in the X direction, you might
want to enter Cs in $DATA, which will necessitate the
input of two more carbon and hydrogen atom, but recovers
use of SYM=.TRUE.
Reference: H.A.Kurtz, J.J.P.Stewart, K.M.Dieter
J.Comput.Chem. 11, 82-87 (1990).
On Wed Sep 14 '11 5:05pm, kaushik hatua wrote
> I am a newcomer in FIREFLY Forum. I like calculate Finite field Calculation of some of the molecules in MP4 level. when i submit the job
>with RUNTYP=FFIELD i got only the Z component of the tensors. can anybody tell me how to arrange the input for getting all the tensor quantities and also using different electric field instead of default 0.001 au field. any suggestion will be appreciated.
>Thanks in advance