Subject: Freq in G94

From: Krzysztof Radacki <[email-masked]>
Date: Thu, 04 Feb 1999 12:33:22 +0000

Dear CCLers,
I have question concerning log from IR calculation in G94.
Below is part of this log:
> Low frequencies ---  -82.8125   -5.2461   -0.0021    0.0021    0.0064    7.1252
> Low frequencies ---   10.1830   65.1288   69.2516
> ******    1 imaginary frequencies (negative signs) ****** 
> Harmonic frequencies (cm**-1), IR intensities (KM/Mole),
> Raman scattering activities (A**4/AMU), Raman depolarization ratios,
> reduced masses (AMU), force constants (mDyne/A) and normal coordinates:
>                     1                      2                      3
>                    A"                     A"                     A'
> Frequencies --   -82.7948                65.1108                69.2511
> Red. masses --     1.0165                 1.0212                 1.1460
> Frc consts  --     0.0041                 0.0026                 0.0032
> IR Inten    --     0.0003                 0.0653                 0.8054
> Raman Activ --     0.0000                 0.0000                 0.0000
> Depolar     --     0.0000                 0.0000                 0.0000
 First frequency is 1A"= -82.7948, and I can also see it in first line
that I gave:
"Low frequencies ---  -82.8125" The second is 65.1108 cm^-1, so my
question what
are this "-5.2461   -0.0021    0.0021    0.0064    7.1252    10.1830" 

In other calculation I can see:
> Low frequencies ---   -9.2092   -8.3593    0.0015    0.0037    0.0040   12.9934
> Low frequencies ---   77.1880   77.8672   96.0089
> Harmonic frequencies (cm**-1), IR intensities (KM/Mole),
> Raman scattering activities (A**4/AMU), Raman depolarization ratios,
> reduced masses (AMU), force constants (mDyne/A) and normal coordinates:
>                     1                      2                      3
>                    A'                     A"                     A'
> Frequencies --    77.1868                77.8275                96.0065
> Red. masses --     1.4137                 1.0145                 1.7426
> Frc consts  --     0.0050                 0.0036                 0.0095
> IR Inten    --     0.8422                 0.2056                 0.2503
> Raman Activ --     0.0000                 0.0000                 0.0000
> Depolar     --     0.0000                 0.0000                 0.0000
And the same question, what are in this case first 7 values?

thanks in advance for any helpfull explanation

       Krzys Radacki

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From: Krzysztof Radacki <[email-masked]>
Date: Thu, 04 Feb 1999 22:07:58 +0100

Dear CCLers,
I would like to thank all people who answerd my question.
Below is one of first answers I get ( from Frank Jensen):
>These are the 6 modes corresponding to overall translation
>and rotation of the molecule. The three 0.00xx modes are the T-modes,
>which should be identically zero, but are not due to numerical
>inaccuracies. The other 3 are the R-modes, which also should be
>zero, but are not since the gradient is not exactly zero. The
>second set of frequencies are obtained by diagonalizing the
>force constant matrix after explicit removal of these 6
>T+R modes.
Once more thank you all.

Regards
      Krzys Radacki
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