[DFTB-Plus-User] Question about hessian generation to use in modes

Bálint Aradi balint.aradi at bccms.uni-bremen.de
Tue Mar 1 16:16:29 CET 2011

Dear Reinaldo,

  sorry for the long delay, I just discovered that your mail had not
been answered yet.

> Secondly, I prepare dftb_in.hsd with the SecondDerivatives option to 
> Driver to generate hessian.out. I append the geometry that was 
> optimized in the previous step, using the *.gen file. But, to my 
> surprise, the job starts with a geometry optimization again before 
> generating the hessian. It took about 30 cycles now, and the problem 
> here is that I cannot get the re-optimized geometry as the 
> OutputPrefix option is not valid in SecondDerivatives.

 When you set Driver = SecondDerivatives, it will relocate each atom a
little bit along the x, y and z axis, in order to calculate the second
derivatives. This is not a geometry relaxation. You see "step" in the
output, but it only indicates which displacement it is doing at the
moment. The Hessian you get, will still belong to the geometry you provided.

  Best regards,


Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen

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