[QE-users] ESM and FCP calculation clarification

[Lucian D. Filip]

Sorry, I meant to say 'bc2'! Not 'bc1'.

On 10/04/2022 11:20, Lucian D. Filip wrote:
>
> Hello all,
>
>
> I am trying to understand the ESM example in the QE github repo. It 
> says in the description that the example is divided in three parts but 
> it doesn't mention it the parts depend on oneanother. Is this the 
> case? I.e. if you don't do the first part of the example then the rest 
> cannot be done?
>
> Another point of confusion if the FCP part of the calculation. Is this 
> a 'relax' type of calculation or can it be performed on a regular 
> 'scf' run?
>
> Also this requirement of a slab to be centered in z=0. It would have 
> been very informative if the example didn't use a 1 atom thin layer of 
> Al for the slab. What is the vacuum region requirement for such a 
> calculation?
>
> I am trying to study a large 1x1xN structure consisting of 
> SrRuO3/PbTiO3/SrTiO3/PbTiO3/SrRuO3 layers of different thicknesses. I 
> would like to consider the 'bc1' case where the structure is 
> surrounded by semi infinite metal electrodes. Do I still need a vaccum 
> region for this case? Or I just construct a 1x1xN supercell centered 
> around z=0 and se the esm_w parameter to 0.
>
> Since my structure involves PbTiO3 which is a ferroelectric with a 
> large bulk polarization, can I use FCP to obtain a correct Hartree 
> potential for this case?
>
> A simple 'scf' calculation on this 1x1xN structure surrounded by 
> vacuum regions, does not converge even after hundreds of steps and no 
> combination of cutoff, k points, mixing beta etc solves this problem. 
> I suspect the problem lies with the effect of polarization and a 
> possible solution would be ESM method (although I expect will take 
> quite a long time).
>
>
> Regards,
>
>
> Lucian
>
>
> P.S.: since the structure is quite large I am not including here an 
> input file but I can provide it upon request.
>
>
> ---
>
> *Dr. Lucian Dragos Filip*
> National Institute of Materials Physics
> Atomistilor str. 405A, PO Box MG. 7
> Magurele, 077125
> Bucharest, Romania
> E-mail: lucian.filip at infim.ro
> Website: https://lucianfilip.wordpress.com/
>
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-- 
*Dr. Lucian Dragos Filip*
National Institute of Materials Physics
Atomistilor str. 405A, PO Box MG. 7
Magurele, 077125
Bucharest, Romania
E-mail: lucian.filip at infim.ro
Website: https://lucianfilip.wordpress.com/
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