[QE-users] Surface-model slab: ESM and definition of a liquid region inside the vacuum

[大谷実]

Dear Mauro,

There are possibly two barriers to an MD calculation with ESM. One is the barrier for electrons, and the other is atoms. The former prevents electrons from leaking into the vacuum region when the surface is negatively charged. The latter prevents atoms from going (evaporating) into the vacuum region.

We usually use a trigonometric function for the barrier of electrons and a parabolic function for atoms. You can find the original function forms in the following reference: Surf. Sci. 601 5237 (2007).

I am not sure such barriers are introduced to QE. At least I haven't implemented it.

Best regards,
Minoru

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National Institute of Advanced Industrial Science and Technology,
Research Centre for Computational Design of Advanced Functional Materials
E-mail: minoru.otani at aist.go.jp
tel : +81-29-861-5202
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________________________________________
From: users <users-bounces at lists.quantum-espresso.org> on behalf of Mauro Sgroi <maurofrancesco.sgroi at gmail.com>
Sent: Saturday, June 27, 2020 7:57 AM
To: Quantum ESPRESSO users Forum
Subject: [QE-users] Surface-model slab: ESM and definition of a liquid  region inside the vacuum

Dear all,
I'm trying to simulate the interface between a charged doped graphene layer and a liquid electrolyte.
I would like to treat the solvent explicitly. So I should place some molecules of the solvent in the vacuum region of my slab model.
I've seen that with the OpenMX code it is possible to use the ESM method and define a potential to confine the liquid in a certain portion of the space between periodic images of the substrate. This prevents the liquid filling all the vacuum space of the supercell during MD.

Here is an explicative figure:
http://www.openmx-square.org/openmx_man3.7/node118.html<https://jpn01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.openmx-square.org%2Fopenmx_man3.7%2Fnode118.html&data=02%7C01%7Cminoru.otani%40aist.go.jp%7C9d3031d5a9ae40fcea8a08d81a2467b2%7C18a7fec8652f409b8369272d9ce80620%7C0%7C0%7C637288090956080025&sdata=ngwDC21Ut6Pdxjmy6lWI2DMkeXHeJRBHk1EtqTtLAjw%3D&reserved=0>

Is something similar implemented in Quantum Espresso?
Or is it possible to obtain it using constraints on the coordinates?

Thanks a lot in advance and best regards,
Mauro Sgroi.
Centro Ricerche FIAT.