[QE-users] using ESM with boundary condition "bc1" for charged slab

[Paolo Giannozzi]

I inquired with the author of ESM and this is what he told me:
"Since BC1 has no screening medium in the system, we need to keep charge 
neutral in the DFT cell. Otherwise, the total energy is diverging. In 
the earlier versions, the manual included a note for such charge 
neutrality condition, but for added safety, a routine to check this has 
been incorporated into the program.

In an ESM-RISM calculation, even when using BC1, there is no need to 
impose the charge neutrality condition in the DFT cell, as the RISM part 
automatically generates a compensating charge to maintain the charge 
neutrality condition throughout the whole system."

Paolo

On 2/9/24 06:07, Ghosh, Prasenjit wrote:
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> 
> Dear all,
> 
> I am performing a calculation for a negatively charged slab using
> assume_isolated = 'esm'
> esm_bc = 'bc1'
> 
> Till qe-7.0 the scf calculation proceeds. However, from version 7.1 the 
> calculation stops with the following error:
> "cannot have charge, when ESM-BC1".
> 
> This is the consequence of a check by the "esm_check" subroutine. What I 
> fail to understand is that this check is also present in qe-6.8, 
> however, there the calculation doesn't stop.
> Am I missing something?
> Also why is this stopped from version 7.1. Are there any issues in the 
> previous versions regarding the implementations of the same? I thought 
> that this is an effective way to perform charged slab calculations.
> 
> Any help in clarifying this will be highly appreciated.
> 
> With regards,
> Prasenjit
> 
> 
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine Italy, +39-0432-558216