[QE-users] assume_isolated=2D

[Thibault Sohier]

Dear Michal, 

The first statement is incorrect: centering the slab around 0 is NOT necessary for the assume_isolated=‘2D’ flag to work. Somehow, it makes more sense intuitively, at least to me, but I guess it depends on how you imagine your cell. Anyway, everything should work fine wherever you put your slab.

The second  statement is almost correct: “the total thickness of the system should be less than half of the Z dimension of the simulation cell” , yes, but the total thickness of the system should also include electrons. So in your next sentence  

"In other words, if Z_dim is the height of the simulation cell, all atoms should be within [-Z_dim/4, Z_dim/4]”

Just replace “all atoms” by "all atoms and all electrons”, and you are good. 

Of course “all electrons” actually means something more like “until the electron density is negligible”.

Thanks, 
Thibault

Post-doc at THEOS, EPFL, Lausanne



> On 25 Apr 2019, at 12:00, users-request at lists.quantum-espresso.org wrote:
> 
> ------------------------------
> 
> Message: 2
> Date: Wed, 24 Apr 2019 17:43:57 +0100
> From: Michal Krompiec <michal.krompiec at gmail.com <mailto:michal.krompiec at gmail.com>>
> To: Quantum Espresso users Forum <users at lists.quantum-espresso.org <mailto:users at lists.quantum-espresso.org>>
> Subject: [QE-users] assume_isolated=2D
> Message-ID:
> 	<CAOWoSSNDWu9bo_C=NWVCO5NNkgXK3hQ8PgsSES4yhjcNmgKpyg at mail.gmail.com <mailto:CAOWoSSNDWu9bo_C=NWVCO5NNkgXK3hQ8PgsSES4yhjcNmgKpyg at mail.gmail.com>>
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> 
> Dear QE Community,
> Could someone clarify if the following is correct: assume_isolated='2D'
> implies that the system (2D slab) should be centered around z=0 and the
> total thickness of the system should be less than half of the Z dimension
> of the simulation cell. In other words, if Z_dim is the height of the
> simulation cell, all atoms should be within [-Z_dim/4, Z_dim/4].
> Thanks in advance,
> 
> Michal Krompiec
> Merck KGaA & University of Southampton

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