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

[大谷実]

Dear Jiri,

As you mentioned, in the aqueous (electrolyte) solution, both anion (COO-) and cation (H3O+) are surrounded by the ionic atmosphere and solvation shell. If you want to describe this effect, you need to introduce water molecules and salt explicitly or introduce implicit solvent such as RISM. 

If your model is correct, the charge separation (H3O+ and COO-) is realized automatically with the ionic atmosphere, even in the 'tot_charge=0' case.

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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On 2020/01/09 4:47, "developers on behalf of Kaňka Jiří" <developers-bounces at lists.quantum-espresso.org on behalf of kanka at ufe.cz> wrote:

    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
    Prague