sorry for a late reply. First of all, you should check whether your geometry optimization has converged. The key words to look for in the output are ***** EQUILIBRIUM GEOMETRY LOCATED ***** If you don't find these words, restart geometry optimization with the atomic coordinates from the last optimization step as an input.
In addition, I'd like to recommend you to add the following non-default options to ensure faster and more stable optimization convergence (see manual for their meaning):
$CONTRL NZVAR=1 COORD=UNIQUE MAXIT=100 fstint=.t. gencon=.t. d5=.t. $END
$statpt METHOD=GDIIS $end
$ZMAT DLC=.t. AUTO=.t. $END
Most options are just added to the existing groups of your input; the exception is COORD=UNIQUE, which should be used instead of COORD=CART.
By the way, RHF/STO-3G is good only for training purposes rather than for real calculations.
If the geometry has converged, the hessian run might have been unconverged. I don't know how to restart an analytical hessian run, which is calculated by default in RHF runs. But I know how to restart numerical hessian, which is calculated by DFT (in case you'll use it). Numerical hessian runs leave file IRCDATA. Just copy it to the end of your input (with optimized atomic coordinates, of course) and add $END line. And replace RUNTYP=OPTIMIZE with RUNTYP=HESSIAN, of course.
Anyway, you don't need to enter $FORCE group (the default values of the keywords in this group are OK)
On Tue Mar 27 '12 10:19am, David wrote
>I am very new to Firefly so apologise if this question is too basic.
>I have tried to solve it through the forums and manual but think perhaps my understanding is insufficient to understand some of the information I have found.
>I am trying to calculate normal modes of vibration for a variety of organics. I have built up my structures and optimised their geometry and wanted to caluclate their vibrational frequencies. The header of my input file looks like this:
> INPUT CARD> $CONTRL SCFTYP=RHF RUNTYP=OPTIMIZE ICHARG=0 MULT=1 COORD=CART $END
> INPUT CARD> $STATPT HSSEND=.T. OptTol=1e-5 NStep=500 $END
> INPUT CARD> $BASIS GBASIS=STO NGAUSS=3 $END
> INPUT CARD> $p2p p2p=.t. dlb=.t. $end
>My runs have terminated normally and the last entry in my output files are $vib but there are no vibrational frequencies.
>Reading in the discussion it seems as if I ought to have used FORCE to get my vibrational frequencies. How to I restart this calculation so the vibrational frequencies are calculated so I can visualise them in MacMolPlt or some other similar visualiser?
>If there is a primer for this kind of thing please accept my apologies and point me in its general direction