Hello all,

I am trying to simulate the effect of strong electric fields on the surface of metals. An external electric field induces a charge on the metal surface and acts on it, straining the metal. Is there a way for me to simulate this process in LAMMPS? I could just apply a force on the surface, but the problem is, if my surface is not flat and some regions have smaller curvature, there should also be locally greater charge density and hence greater pulling force.

Any help is appreciated.

Kristian Kuppart

Hello all,

I am trying to simulate the effect of strong electric fields on the surface of metals. An external electric field induces a charge on the metal surface and acts on it, straining the metal. Is there a way for me to simulate this process in LAMMPS?

Have you studied this setup with a quantum code? It would be difficult to model the effect of the external field in an empirical model without having anything to calibrate it with. If it is at all possible.

I could just apply a force on the surface, but the problem is, if my surface is not flat and some regions have smaller curvature, there should also be locally greater charge density and hence greater pulling force.

Thank you for your reply. I have not, because the system under investigation is quite large, on the order of few million atoms so that it would be thick enough that different finite size effects would be reduced. One way we have considered is Finite Element analysis for the surface charge, coupled to dynamics in LAMMPS. The Wish List on the LAMMPS website lists, among others "*Coupling to finite elements for stress-strain"* which states*,* that lammps could then be coupled to finite elements for stress/strain or *“other kinds of PDE effects”*

Is electrodynamics also meant as part of this package under development?

Best regards,

Kristian Kuppart

Thank you for your reply. I have not, because the system under investigation

is quite large, on the order of few million atoms so that it would be thick

it is good practice to first study an effect like you describe with a

small model. if it is not possible to find a good representation on

this small scale, it would be a waste of time to go to a larger scale.

enough that different finite size effects would be reduced. One way we have

finite size effect are irrelevant in this case, as they would apply to

the empirical model just as well as to the QM calculation. but if you

don't know what is the process on the smallest level, how can you

expect to describe it correctly on a larger scale?

considered is Finite Element analysis for the surface charge, coupled to

dynamics in LAMMPS. The Wish List on the LAMMPS website lists, among others

"Coupling to finite elements for stress-strain" which states, that lammps

could then be coupled to finite elements for stress/strain or "other kinds

that is something completely different and likely more suitable for

the kind of effect you are describing.

of PDE effects"

Is electrodynamics also meant as part of this package under development?

you have to ask the authors of the AtC package this question. ...and

again, you first need a way to parameterize the effect and model that

represents it well enough.

axel.