Subject: Gaussian98W and hessian again....

From: Connie Chang <[email-masked]>
Date: Wed, 18 Dec 2002 16:47:46 -0500

Hi --

I was wondering if someone could answer two questions I have about
Gaussian's output where the hessian is concerned...

 I obtained the hessian from the archive portion of the output file
starting from NImag=0|| and ending at ||.  I read this is as lower
triangular matrix and filled in the blanks.  THen I converted it to
units of erg/cm^2 and divided by the mass (my molecule contains all of
the same atoms).  Then I diagonalize this matrix to get the eigenvalues
and eigenvectors.  My question is -- Why don't the eigenvectors I get
this way match the eigenvectors given by the output part of the file:
                           6         7         8         9        10
                          AG        BU        AG        BG        AU
       Frequencies ---   133.7777  217.8831  219.3526  220.1136
220.5401
    Reduced masses ---    12.0000   12.0000   12.0000   12.0000
12.0000
   Force constants ---     0.1265    0.3356    0.3402    0.3426
0.3439
    IR Intensities ---     0.0000    0.0109    0.0000    0.0000
0.0086
  Raman Activities ---     0.0000    0.0000    0.0000    0.0000
0.0000
   Depolarizations ---     0.0000    0.0000    0.0000    0.0000
0.0000
 Coord Atom Element:
   1     1     6          0.06549   0.02995  -0.02972   0.00000
0.00000
   2     1     6          0.00350  -0.02940   0.01482   0.00000
0.00000
   3     1     6          0.00000   0.00000   0.00000   0.04056
-0.03387
   1     2     6          0.06720  -0.00807   0.00067   0.00000
0.00000
   2     2     6          0.00539  -0.02838  -0.00791   0.00000
0.00000
   3     2     6          0.00000   0.00000   0.00000  -0.00920
0.00683
   1     3     6         -0.05283  -0.00382   0.00879   0.01422
-0.01471
   2     3     6          0.02203   0.00592   0.00998  -0.00374
0.00309
   3     3     6          0.00014  -0.00365   0.00415  -0.01084
0.00751

etc.etc.?  I need the entire eigenvector matrix and not just 3*N-6
translation/rotational modes.  The eigenvalues seem to match up fine,
but the eigenvectors are different.  Am I somehow scrambling the atom
order or something?

I've heard that Gaussian prints out the hessian as well using some IOP
option.  Does anyone know the exact option?

Thanks,

Connie