[CPMD-list] about hessian maatrix

[Axel Kohlmeyer]

On 9/16/06, Hiroshi Fujisaki <fujisaki at bu.edu> wrote:
> Dear Axel,

dear hiroshi and yong,

[...]

> I have a few questions about hessian calculations in CPMD.
>
> 1) Is it calculated by analytical means or numerically?

the hessian is calculated (incrementally) from the forces
and atom positions, 'numerically'  from spline interpolation. so...

> 2) Is it calculated on a Born-Oppenheimer surface? OR
>    is there any contribution from "fictious" electron dynamics?

since the hessian is (currently) only calculated during geometry
optimization, there is no contribution from a fictitious 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 ...

my only comment on that is: 'use the source, luke'
  ;-)

cheers,
   axel.
>
> I appreciate your comments.
>
> Best wishes,
>
> --
> Hiroshi Fujisaki <fujisaki at bu.edu>
>
>


-- 
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Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
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