[gmx-users] Electric double layer, how to add charge

[André Farias de Moura]

you should edit your topology file (either top or itp) to include explicit
charges to each atom.

regarding the proper choice of charges, it depends on the surface potential
you think your system should have (mind that OPLSAA will typically produce
an overestimated potential as compared to experiment, if available - from
my experience it may be 2-3 times larger)

adding charges with opposite signs in different layers work as well, you
just need to keep track of the layer in which each atom is located and then
edit the topology files accordingly (in this case, you'll have a neutral,
polar interface, as compared to the electrically charged interface obtained
using only charges of the same sign)

best

André

On Wed, Sep 16, 2015 at 5:45 PM, Andreas <adnad at gmx.net> wrote:

> Hello users,
>
> I want to simulate a graphene electric double layer (edl). So far i have
> used the cnt tutorials and the tutorial for lysozyme in water.
> All modification to the OPLSAA field parameter (atomname2type.n2t,
> atomtypes.atp, ffbonded.itp, ffnonbonded.itp) which i have done were with
> zero charge and i could already simulate a graphite layer in a box filled
> with water and ions, similar to the lysozyme tutorial.
>
> How and then to add a charge to the graphene layer, or if two graphene
> layers are added, how to add opposite charges to them?
>
> Or is there a more simple way to MD simulate an edl, in gromacs,
> altogether?
>
> I would be very thankful for any help
>
> Best regards
>
> Andreas
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-- 
_____________

Prof. Dr. André Farias de Moura
Department of Chemistry
Federal University of São Carlos
São Carlos - Brazil
phone: +55-16-3351-8090