[CP2K:10631] electrostatic decoupling

[Xiaoming Wang]

Dear Prof. Hutter,

Thanks for your explanations and suggestion. I will read the 
corresponding papers. Btw, does the ddapc method solve
this problem? There is a 'e_decpl' decoupling energy in the 
cp_ddapc_apply_CD. Or it still suffers the same
problem?

Best,
Xiaoming


On Thursday, August 16, 2018 at 8:12:32 AM UTC-4, jgh wrote:
>
> Hi 
>
> your problem is related to the ill-defined energy of a charge 
> in a periodic system. 
> Your energy 1 is calculated with a background charge to nuetralize 
> the charge of your orbital. In energy 2, the isolated system, 
> no such background charge is needed. 
>
> If you want to get some idea how to attack this problem, I would 
> suggest to read the vast literature on the calculation of 
> charged defects in solids. Start with the recent work of Pasquarello. 
>
> regards 
>
> Juerg 
> -------------------------------------------------------------- 
> Juerg Hutter                         Phone : ++41 44 635 4491 
> Institut für Chemie C                FAX   : ++41 44 635 6838 
> Universität Zürich                   E-mail: hut... at chem.uzh.ch 
> <javascript:> 
> Winterthurerstrasse 190 
> CH-8057 Zürich, Switzerland 
> --------------------------------------------------------------- 
>
> -----cp... at googlegroups.com <javascript:> wrote: ----- 
> To: "cp2k" <cp... at googlegroups.com <javascript:>> 
> From: "Xiaoming Wang" 
> Sent by: cp... at googlegroups.com <javascript:> 
> Date: 08/15/2018 10:05PM 
> Subject: [CP2K:10631] electrostatic decoupling 
>
> Hello, 
>
> I'd like to decouple the the Coulomb interaction between the electron of 
> one specific state, say HOMO, 
> and its periodic images, for a fully periodic DFT calculation. The 
> interested charge density is localized. 
> I have tried to use different poisson solvers, say MT or WAVELET, to 
> achieve my goal. So first I extracted 
> the the charge density from mo_coeff. Then called the poisson solver. 
>
> pw_poisson_solve(poisson_env, orb_rho_g%pw, ener1, v_gspace1%pw) 
>
> with poisson environment PERIODIC3D. Next I changed the poisson_env to 
> MT0D, then called  poisson 
> solver once more. 
>
> pw_poisson_solve(poisson_env, orb_rho_g%pw, ener2, v_gspace2%pw) 
>
> Finally, the decoupling energy is deltaE = ener1 - ener2. I thought deltaE 
> should be a very small 
> number, because the charge density of that state is quite localized and my 
> unit cell is big enough for 
> the MT solver. However, I got a very large deltaE 0.05 Ha. Also the value 
> is negative, which means the 
> Hartree energy is higher for the decoupled case. I cannot understand this, 
> because I think the image 
> interaction would increase the energy. So can anyone give some advice? 
>
> Best, 
> Xiaoming Wang   
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