[Pw_forum] static dielectric constant (esp_0)

[Stefano Baroni]

Dear Hanghui:

example 31 deals with bulk silicon, a bulk, nonpolar, system for which  
\eps_\infty=\eps_0
the result you get is what you should expect. technically, the  
vanishing forces on atoms are due to the vanishing ionic (Born)  
effective charges, which in turn is due to the tetrahedral point  
symmetry of atomic sites
Cheers - SB

On Jul 23, 2008, at 2:34 AM, alan chen wrote:

> Dear PWSCF users,
>       I am now trying to calculate the static dielectric constant  
> (esp_0). From the example31 in the espresso4.0 package, I know that  
> by doing two self-consistent calculation with E=0 and E=0.001a.u. (E  
> is an external homogeneous electric field), we can get esp_{inf}  
> i.e. the ions do not respond to the electric field. Now since I want  
> to calculate esp_0 (include the response of ions), I relax all the  
> atoms by using 'relax'. However, I found that all the forces on the  
> atoms are zero even if I turn on electric field. So how to calculate  
> static dielectric field (esp_0) ? Why are the forces zero even when  
> the external electric is turned on?
>       Thank you very much.
>
> Hanghui
> Department of Physics
> Yale University
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---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
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