[lammps-users] to calculate electric fields of graphene/metal composite materials with LAMMPS

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Dear LAMMPS users,

Hello, This is a student who wants to get electrical properties of graphene/metal composite materials with LAMMPS. I have previously obtained mechanical properties such as stress sensors with LAMMPS, and I have found that thermal analysis of thermal properties has many papers, so I know that mechanical and thermal MD analysis is possible with LAMMPS. However, I did not find any papers or research on electrical analysis using only LAMMPS. Therefore, I thought that electrical properties could not be obtained by LAMMPS. However, after confirming that ‘fix field command and dump ex ey ez results’ are being dealt with in the LAMMPS manual, I found that electric fields between atoms of materials are available to compute, although electrical analysis such as DFT and ab-initio cannot be computed in LAMMPS. So I’m trying to use the fix efield command to create scripts to get ex, ey, and ez as a dump file. But I’m having a hard time with this. I’m thinking about whether the reason I’m having a hard time is because of my lack of coding skills in dealing with LAMMPS, or if my attempt to compute electric fields with LAMMPS is wrong in the first place. My goal is to obtain electrical properties of materials that I want to analyze with MD analysis tool, LAMMPS, and I want to get the result of the electric field that I think is possible at LAMMPS. If I could get help from experts who already know how to handle LAMMPS, it would be very helpful for my research direction.

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I think you are mistaken in a) what it is that fix efield does and b) how the potentials in LAMMPS compute forces.

For the most part the situation is rather different form electronic structure calculations since the major point of classical models is to avoid those, so a lot of tools and properties that can be computed from a DFT calculations are not explicit in such calculations with classical models and thus cannot be easily extracted.

fix efield is effectively just adding a force that is scaled by an assigned partial charge of an atom, but with most metals, those are not explicit and thus not available and also the (highly mobile and polarizable) electrons of a metal are only modeled in an approximate and implicit way.

Axel.