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, [email protected] wrote: > > ------------------------------ > > Message: 2 > Date: Wed, 24 Apr 2019 17:43:57 +0100 > From: Michal Krompiec <[email protected] > <mailto:[email protected]>> > To: Quantum Espresso users Forum <[email protected] > <mailto:[email protected]>> > Subject: [QE-users] assume_isolated=2D > Message-ID: > <CAOWoSSNDWu9bo_C=nwvco5nnkgxk3hq8pgsses4yhjcnmgk...@mail.gmail.com > <mailto:CAOWoSSNDWu9bo_C=nwvco5nnkgxk3hq8pgsses4yhjcnmgk...@mail.gmail.com>> > Content-Type: text/plain; charset="utf-8" > > 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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