[Pw_forum] Perturbation in electronic field

[Stefano Baroni]

On Oct 10, 2008, at 3:58 AM, yumin qian wrote:

> There is one problem I am not clear about DFPT in external  
> electronmagnetic field. How to switch on the external field since  
> the field will distroy the translational symmetry(periodic boundary  
> condition ).

please, take the time to have a glance at:
S. Baroni, S. de Gironcoli, A. Dal Corso, and P. Giannozzi, Phonons  
and related crystal properties from density-functional perturbation  
theory, Rev. Mod. Phys. 73, 515 (2001).


>
> There a two way right now : one is add a dipole layer in vaccum  
> layers , this method can only be used in slab calculation
>
> the other is to add a periodic field and at the end make the  
> periodic to infinite (long wave appriximation). Vanderbilt also made  
> a proposal using the Berry phase approach,

third, DFPT (restricted to the linear, or low-order) regime

>  My question is in PWSCF how the electronic field is added ,

through either of the first two methods. the third is implemented in  
PHONON

> and whether the method can be used in metal system ?

homogeneous electric fields in a metal? for that a computer code is  
not enough. One should modify Maxwell's equations!

SB

---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
Trieste
http://www.sissa.it/~baroni / [+39] 040 3787 406 (tel) -528 (fax) /  
stefanobaroni (skype)

La morale est une logique de l'action comme la logique est une morale  
de la pensée - Jean Piaget

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