[lammps-users] Convert setfl format potential file to funcfl format

Hi, everybody,

I’ve been trying to convert the EAM potential of Co in the setfl formatted “CoAl.eam.alloy” file to a separate funcfl formatted “.eam” file. It seems that the only problem lying behind is the pair potential. In setfl format it is expressed as "rphi" and in funcfl it is expressed as “effective charge Z”
After reading the lammps manual and the “pair_eam.cpp”, “pair_eam_alloy.cpp” files, I though I found the relation between the above expressions:
r
phi = 27.2 * 0.529 * Zi * Zj (http://lammps.sandia.gov/doc/pair_eam.html)
For the interaction of same kind of atoms at certain distance, this relation seems hold: Z^2 = rphi/(27.20.529). And the right hand side of this equation seems non-negative.
But in the “CoAl.eam.alloy” file, the r*phi function has negative values!
Hence, it brought up the following questions, I’d really appreciate it if someone can help me with them.

  1. Is there a way to convert the potential of a single element in the setfl formed file into a funcfl formated file?

  2. If my statements above are true, then when lammps is dealing with funcfl files, for the interaction of the same kind of atoms are the calculated r*phi values non negative?

Thanks,

I think the alloy setfl format is more general and may allow for
the negative values. So there may be no way to convert
that one to funcfl format. You might try an email to Chandler.Becker
at nist.gov
who maintains an archive of EAM potential files on his WWW site (listed
in the pair eam doc page.

Note that you can use a setfl file for a single element simulation in LAMMPS,
you don't have to use a funcl file.

Steve

Hi, Dr. Plimpton,
I was trying to use the “mixing” feature in the funcfl format for more than one elements, not to model a single element. But thanks for the information. I will contact Dr. Becker for her opinion.