[QE-developers] defining ions charges for QE-ESM-bc1

Kaňka Jiří kanka at ufe.cz
Wed Jan 8 20:46:48 CET 2020

Dear QE-ESM developers,

ESM with bc1 is fine for the investigation of changes in the working functions of gold electrodes functionalized with
self-assembled monolayers (SAM) of alkanethiols. For characterizations of the modified electrodes
is useful to include also the SAM/aqueous solution interface. When pH of the solution is increased to 8,
the SAM monolayer is deprotonated and becomes negatively charged  which is compensated  contra-ions in solution arising
from dissociated protons (RCOOH + H2O > RCOO- + OH3+).  The increased dipole over the SAM/solution contributes
to a total surface dipole and therefore effects the work function.

The problem is how to set the charges of COO- and OH3+ ions when in the input file is possible to define only a total charge
(here it is 0 which should allow to use bc1).

Thank you.

Best regards,
Jiri Kanka

Optical Biosensors
Institute of Photonics and Electronics
Czech Academy of Sciences

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