[Pw_forum] help about electric field energy

[Andrea Dal Corso]

On Mon, 2005-03-21 at 11:49 +0800, xywu wrote:
> Dear All,
> 
>   I've some questions about electric field in pwscf.
>   For example, a typical pw.x outfile with sawlike electric field is as 
> follows:
> 
> " total energy              =   -28.51347695 ryd
>       estimated scf accuracy    <     0.00000015 ryd
> 
>       band energy sum           =    -1.13799379 ryd
>       one-electron contribution =  -182.11215176 ryd
>       hartree contribution      =    97.79164443 ryd
>       xc contribution           =   -11.20951092 ryd
>       ewald contribution        =    66.27671809 ryd
>       electric field correction =     0.74246200 ryd
>       correction for metals     =    -0.00263879 ryd
> 
>       convergence has been achieved
> "
> 
> I want to konw whether the "electric field correction" is the electric 
> filed energy in the system.

Unfortunately it is not. It is just the ionic contribution to the
electric field energy since the electronic contribution is already
contained in the sum of the eigenvalues (band energy sum).


>  If it's not, how to get the electric filed 
> energy and electric field strength in the system from pp.x.

Presently you can calculate the surface dipole density if you have a
slab or the dipole moment if you have a localized charge by using pp.x
and chdens.x. If you need the electric field energy you should 
calculate it yourself. (Please look at the routines add_efield and
compute_dip)

Hopefully, this will be improved by somebody in the next future.

Andrea

> 
> Please give me some advice.
> 
> Thank you in advance!
> 
-- 
Andrea Dal Corso                    Tel. 0039-040-3787428
SISSA, Via Beirut 2/4               Fax. 0039-040-3787528
34014 Trieste (Italy)               e-mail: dalcorso at sissa.it