The ABINIT Users Mailing List ( CLOSED )

[Xavier Gonze <gonze@pcpm.ucl.ac.be>]

On 11 Aug 2006, at 04:23, yunhee.chang@kriss.re.kr wrote:

> Dear Abinit users,
>
> I'm calculating the phonon dispersion band of In/Si(111) surface.
> At that time, I'm using the linear response theory in Abinit.
> In the response function calculation, there are rfphon, rfatpol,  
> rfdir, rfelfd options.
> But there is no the parameter to control the quantity of perturbation.
> I think, when I use the rfdir option, the direction of displacement  
> is controled.
> But how much the atomic position is moved???
> How much the charge density is perturbed??
> Maybe the default value is present in the program,
> where can I know this parameter's information.
>
> Would you give me any comments?

Please, consider reading my mail of June 19, answering a similar  
question
on the mailing list ...

Xavier

On 19 Jun 2006, at 12:05, javier.torres@unito.it wrote:

> Dear Abinit users...
>
> Someone knows if it is possible to define the magnitude of the  
> atomic displacement in a phonon calculation???

No, this is not needed.
ABINIT does not use the frozen-phonon formalism, but linear-response,  
in which there is no notion
of the magnitude of the atomic displacement : the calculation  
addresses directly the computation
of the second-derivative of the total energy ... Linear-response is  
more direct than frozen-phonon.
Please read the relevant litterature, e.g. those that you will find  
under the heading
"Response function computation" in the page
http://www.abinit.org/Infos_v5.1/users/bibliography.html

Xavier