[Pw_forum] DCC correction to electrostatic potential

[e kb]

Dear Hai-Ping
Nick is right, DCC for partial periodicity is not in the cvs version of the code yet. 
The main issue is not the "whichbc" parameter that you've checked in the Multigrid directory. The way that the true potential is calculated (add_boundary.f90) and Poisson equation that is solved should be modified accordingly (add_dcc_field.f90).
Regards, 
 
Emine Kucukbenli, 
grad student, SISSA, Italy.

--- On Thu, 2/19/09, lan haiping <lanhaiping at gmail.com> wrote:

From: lan haiping <lanhaiping at gmail.com>
Subject: Re: [Pw_forum] DCC correction to electrostatic potential
To: "PWSCF Forum" <pw_forum at pwscf.org>
Date: Thursday, February 19, 2009, 4:12 AM


Dear Nick, 
Thanks.  
Therefore, My problem is just due to wrong BC handling by QE. I found the settings for boundary conditions at $QE/Multigrid, and just thought it should be OK for all possible aperiodic situations.
Would you mind to tell me 
which subroutine in $QE/EE accounts for boundary settings ?

Regards,
Hai-Ping


On Thu, Feb 19, 2009 at 1:20 AM, Nicholas E. Singh-Miller <nedward at mit.edu> wrote:

Dear Hai-Ping,

I am looking at espresso-4.1CVS.

Looking at the subroutines in EE/, it looks like the DCC correction is
currently only coded for isolated systems -- in which case the
calculataion of BCs for a CNT would cut through the charge density. (but I
could be missing something).

Regads,

Nick


On Wed, 18 Feb 2009, lan haiping wrote:

> Dear All,
>
>  I did test calculations on DCC correction implemented in CVS version.
> I came to  problems when i examine the results of electrostatic potential.
> Would you please give me some hints ?
> My test calculation is a CNT (10,10)  system,  and the setting for
> DCC correction is
>        which_compensation ='dcc',
>        ecutcoarse = 100.0,
>        n_charge_compensation= 5,
>        nlev = 4,
>        whichbc(1)= 0, whichbc(2)=0,
>        whichbc(3)=1,
> But the final fermi energy i obtained is -3.99 eV, which is not consistent
> with
> previous report on workfunction of CNTs(about 4.6 eV ).
>
> Best,
> Hai-Ping
>
>
>

*****************************************
Nicholas E. Singh-Miller
Ph.D. Candidate
Prof. Marzari Group (quasiamore.mit.edu)
Materials Science and Engineering
Massachusetts Institute of Technology
13-4066
(617)324-0372
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-- 
Hai-Ping Lan 
Department of Electronics ,
Peking University , Bejing, 100871
lanhaiping at gmail.com, hplan at pku.edu.cn
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