[Octopus-devel] cvs commit: marques/octopus/src epot.F90epot_inc.F90 f_inc.F90 h.F90 h_inc.F90 h_so.F90 lcao.F90td_exp_split.F90

[Miguel Marques]

Sex, 2005-07-29 às 12:28 +0200, Angel Rubio Secades- escreveu:
> Hi;
> 
> Forces for phonons:
> we don't need to move the grid with the atom, therefore we could get the 
> phonons as we did before.
> Furthermore, we could get them with the linear-repsonse approach (as it is 
> done for the polarisability by Eugene)


Hi Angel,

I disagree to some extent! Yes, we can do linear response (actually it
was the thing I had in mind). However, this is only possible if the
Pulay forces are small. Otherwise, the dynamical matrix will include an
error we can not account for. Of course, the Pulay forces decrease to
zero with the size of the basis. We really have to make all these tests
before knowing for sure what we're up to.

  cheers,
  miguel