Question about potential field for Aluminum graphite material

Hi all,

I have an aluminum block enforced by a sheet of graphite which I’m trying to model the friction of this material on a sheet of rigid body. I was wondering what kind of potential field would be the best for this combination?

Since I’m a newbie in LAMMPS any kind of suggestions/helps would be much appreciated.

Hi all,

I have an aluminum block enforced by a sheet of graphite which I'm trying to
model the friction of this material on a sheet of rigid body. I was
wondering what kind of potential field would be the best for this
combination?

Since I'm a newbie in LAMMPS any kind of suggestions/helps would be much
appreciated.

your question is not really about LAMMPS but about the science of your
problem. thus the best way to find an answer is to study the published
literature for similar calculations. since you are new to LAMMPS you
first will have to learn how to use it correctly and that is usually
best confirmed by reproducing already published results with it. if
you are also a newbie in MD, then i recommend to learn basic MD
techniques as well.

please keep in mind, that LAMMPS provides the tools, but not the
science, and its mailing list is no replacement for doing your
"homework".

axel.

Dear Axel,

First off, thank you so much for your response.
I believe I asked my question in a wrong way.

Lets try it in this way:

My model has two different atoms (Al and C), for the aluminum part I’m using eam potential (Al99.eam.alloy as the potential coeff) and for the graphite (lj/cut/coul/long). So I want to use the hybrid pair style as( pair_style hybrid eam/alloy lj/cut/coul/long 10.0) but I’m getting error of (ERROR: Pair coeff for hybrid has invalid style (…/pair_hybrid.cpp:351)).
First I thought maybe I’m choosing wrong potentials and the whole setting was wrong but I just found another post in the mailing list with the same problem which apparently was a bug in the code (http://lammps.sandia.gov/threads/msg35237.html). Now, if I want to correct myself, can you please give me any suggestion with my code to see where am I doing wrong which causes this problem:

Hybrid force fields

pair_style hybrid eam/alloy lj/cut/coul/long 10.0

pair_coeff * * Al99.eam.alloy Al
pair_coeff 2 2 lj/cut/coul/long 0.068443 3.407

Thanks again for your help.

Dear Axel,

First off, thank you so much for your response.
I believe I asked my question in a wrong way.

Lets try it in this way:

this is not a different way, this is a *completely* different
question. who are you trying to kid here?

My model has two different atoms (Al and C), for the aluminum part I'm using
eam potential (Al99.eam.alloy as the potential coeff) and for the graphite
(lj/cut/coul/long). So I want to use the hybrid pair style as( pair_style
hybrid eam/alloy lj/cut/coul/long 10.0) but I'm getting error of (ERROR:
Pair coeff for hybrid has invalid style (../pair_hybrid.cpp:351)).
First I thought maybe I'm choosing wrong potentials and the whole setting
was wrong but I just found another post in the mailing list with the same
problem which apparently was a bug in the code
(http://lammps.sandia.gov/threads/msg35237.html). Now, if I want to correct
myself, can you please give me any suggestion with my code to see where am I
doing wrong which causes this problem:

the thread you are referring to is *not* about a bug.
the problem is simply that your input is not according to the
requirements of the hybrid pair style. it is missing the style
designation that matches the pair_coeff parameters with the specific
style. this is a trivial error and has been much discussed here. you
can easily find the offending input line by using the -echo screen
flag. a technique that is discussed in the section of the manual about
finding errors in your input..

please keep in mind that 99.9% or more of errors that beginners make
are due to mistakes, typos, or sloppy reading of the manual. they are
extremely rarely due to a bug in LAMMPS or a bad choice of potential.

axel.