Author Topic: statpt & hessian read  (Read 6368 times)

chburger

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statpt & hessian read
« on: July 08, 2007, 08:48:23 pm »
I inquired a problem with statpt:

While aoforce clearly evidenced only one imaginary frequency, statpt (V5-9-1 18 Apr 2007) believes that there
are two: Do I miss something here?

Regards

Peter

relevant part of the control file:
 
$nvibro       93
$vibrational spectrum
#  mode     symmetry     wave number   IR intensity    selection rules
#                         cm**(-1)        km/mol         IR     RAMAN
     1        a           -1078.97         0.00000       YES     YES
     2                        0.00         0.00000        -       -
     3                        0.00         0.00000        -       -
     4                        0.00         0.00000        -       -
     5                        0.00         0.00000        -       -
     6                        0.00         0.00000        -       -
     7                        0.00         0.40029        -       -
     8        a              56.97         1.10216       YES     YES
     9        a              80.77        11.72408       YES     YES
    10        a              84.74         3.16747       YES     YES


statpt output:

  Found initial Hessian matrix in $hessian section
  Number of zero Hessian eigenvalues:   0

   5 first eigenvalues:
 -0.06471367 -0.05304723  0.00080796  0.00150790  0.00939792

  Eigenvalue of transition vector: -0.06471367

                  #######################################
                   WARNING: HESSIAN HAS WRONG INERTIA!!!
                      NUMBER OF NEGATIVE EIGENVALUES
                                    2
                  #######################################

turbomaster

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Re: statpt & hessian read
« Reply #1 on: July 09, 2007, 10:19:07 am »
What you see in the output of aoforce are vibrational frequencies, i.e. square roots of eigenvalues of the mass weighted Cartesian Hessian. In the statpt output you see the eigenvalues of the Hessian matrix in internal coordinates. Although usually there is a close correspondence between vibrational frequencies and normal modes of internal Hessian this need not to be always the case.