[CPMD-list] about hessian maatrix

[Hiroshi Fujisaki]

Dear Axel,

> > used for later calulations. I want to use the hessian matrix from a
> > "geometry optimization" to do some analysis. And (1) how can I extract the
> > hessian from the restart file and make it "readable" for my own code or (2)
> > is this information available and accessible easily in other files?
> 
> the (nuclear) hessian is stored in a file called (tada...) HESSIAN
> which is directly readable as it is formatted.
> please see the files hessout.F and hessin.F for details.

I have a few questions about hessian calculations in CPMD.

1) Is it calculated by analytical means or numerically?
2) Is it calculated on a Born-Oppenheimer surface? OR 
   is there any contribution from "fictious" electron dynamics?
3) Can we calculate a hessian while we are doing a MD simulation?
   (I mean, without minimization) In this case, we, of course, 
   have imaginary frequencies but we sometimes use such quantities 
   in MD simulations ...

I appreciate your comments.

Best wishes,

-- 
Hiroshi Fujisaki <fujisaki at bu.edu>