The ABINIT Users Mailing List ( CLOSED )

[Philippe GHOSEZ <Philippe.Ghosez@ulg.ac.be>]

Hi Aldo and Matthieu,

Yes, the scissors option is used in response function.

Since it is a rigid shift of the conduction bands, you can do it by hand
at the level of the electronic bandstructure when you plot it.

As mentioned by Matthieu, it is mainly used in the calculation of the
optical dielectric constant but it was also applied for non-linear 
optical
suscepitibilities and eletro-optic coefficients. You can have a look at 
:

M. Veithen, X. Gonze and Ph. Ghosez, Phys. Rev. B 71, 125107 (2005).

Best wishes,

Philippe.

On 01 Aug 2008, at 18:18, matthieu verstraete wrote:

> Hi Aldo,
>
> as you shrewdly detected the sciss is only used for the resp function 
> part. The output band structure comes from the ground state bits of 
> abinit, and does not depend on sciss. This might be changed to include 
> a nice aesthetic shift, but it wouldn't affect the calculation itself. 
> In the calculation of phonons or other perturbations, sciss comes in 
> every time the GS eigenvalues are reused, in particular in:
>
> abinit-5.6.x/src/16response/cgwf3.F90
> abinit-5.6.x/src/16response/eig2tot.F90
> abinit-5.6.x/src/16response/vtowfk3.F90
>
> if you care to look.
>
> Basically they intervene in the  Sternheimer equation (eq 16 of 
> Xavier's prb 55 10337) and the variational expressions for the 2nd 
> order energies (eq 15 of Xavier's PRB 55 10355), and that is where the 
> sciss is added in. It works, and you have to pass the sciss on to 
> anaddb as well for the optical properties (as I remember this is 
> automatic through the ddb files). I think it should only be used for 
> q=Gamma for rfelfd 3, ie phonons with LOTO splitting.
>
> Has anyone used sciss for third order responses (Raman etc)?
>
> Ciao
>
> Matthieu
--------------------------------------------------
Prof. Philippe GHOSEZ
Universite de Liege
Institut de Physique, Bat. B5
Allee du 6 aout, 17
B- 4000 Sart Tilman
BELGIUM

Phone : ++(32) (0)4-366.36.11
Fax   : ++(32) (0)4-366.36.29
E-mail: Philippe.Ghosez@ulg.ac.be

http://www.ulg.ac.be/phythema
--------------------------------------------------