RE: Eigenvalues of hessian

Some numerical methods use small perturbations in the x, y and z planes to
 compute force constants. Unfortunately this effectively contaminates the
 calculation with net translations. Could this be happening in your Hessian calc?
 James (if I wrong, do let me know!)
 -----Original Message-----
 From: Computational Chemistry List [mailto:chemistry-request.-at-.ccl.net]On
 Behalf Of Daniel R. Rohr
 Sent: 28 May 2003 15:21
 To: ccl
 Subject: CCL:Eigenvalues of hessian
 Hi CCLers
  Does anybody of you know, why there are more than 3N-6 nonzero
 eigenvalues of the hessian? I am especially interested in the question,
 whether this error is due to the errors made by differentiation or
 whether they are due to an error within the method itself. I usually get
 only 3 zero eigenvalues. No matter if the hessian is calculated on a
 stationary point or not.
 Thanks for your help
 Daniel Rohr
 --
 -----------------------------------------------------------------------
  Daniel Rohr                                    Fachbereich Chemie der
                                                 Philipps-Universitdt
  Tel.: +49-6421-28-25686                        Hans-Meerwein-Stra_e
  Fax.: +49-6421-28-25566                        D-35043 Marburg
  eMail: rohrd.-at-.stud-mailer.uni-marburg.de        Germany
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