[lammps-users] platinum-water interaction potential

You all might be interested in looking at the “Charge Optimized many-body” COMB potentials developed by Susan Sinnott and Simon Phillpot. It is basically a Tersoff type potential that includes charge optimization and equilbration via the Stuart and Rick fluctuating charge method. I think this is the same method used by REAXFF for charge equilibration. Sinnott and Phillpot currently have potentials for SiO and Si-O-Cu and a few other metals (but no water as of yet). REAXFF would be another good place to look, but it would need parameterization for your system. It would make a great PhD project for somebody. As with any new potential parameterization, this takes a lot of time and thought. Don’t expect results overnight.

If you are willing to ignore all the interesting chemistry, you could just assign fixed point charges to the metal surface and run using lj/cut/coul/cut.

Good luck.

Hi, Dave

I am interested in just assigning fixed point charges to the metal surface as you suggest, could you suggest me some reference paper about it? I need to know the detail of how to do this.

Thanks a lot.

ziyuan

ziyuan,

I haven’t seen a specific paper for your problem. But I can give you an idea where to start. You would need to first find a good guess for the surface charge on the metal. If you can’t find it in the literature, it might require doing some DFT calculations on your own to get an idea what the charge distribution looks like. You’ll also need to figure out good LJ parameters for Pt-O and Pt-H (though you might get away with ignoring Pt-H). If you can find any experimental or DFT papers describing the structure of water in the presence of Pt you can try to fit your parameters to that.

From there it’s just an issue of making lammps to what you need it to do. You’d need a hybrid potential tip4p for H2O, EAM for Pt, and lj/cut/coul/cut for the cross potentials.

I’m working on a similar script for H2O + Au nanoparticles based on one I found on the mailing list archives. I’ll send it to you when it’s finished. You may be able to use it as a starting point.

Just keep in mind that you are ignoring some important H2O+Pt chemistry by going this route!

Dave

We have an initial implementation of COMB for LAMMPS from
a grad student in Sinnott/Phillpot's group. We plan to release
it in LAMMPS soon.

Steve

Hi, Dave

I am not majored in Chemistry. So I have a question that why metal surface will be charged when it contacts with water?

ziyuan

This is a classic E&M problem. Wikipedia has a good page on it.

http://en.wikipedia.org/wiki/Method_of_image_charges

Matt

Quoting shiziyuan <[email protected]>: