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Re: Finite Field Calculation in MP4

Alex Granovsky
gran@classic.chem.msu.su


Dear Kaushik Hatua,

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
                       (default=0.001 a.u.)

         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
           wavefunction.

         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
         wavefunction evaluations.

             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).


Kind regards,
Alex Granovsky

On Wed Sep 14 '11 5:05pm, kaushik hatua wrote
---------------------------------------------
>Dear all,
> 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


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