The Embedded Atom Method (EAM) is a multibody potential developed by Daw and Baskes [1, 2]. Steven Foiles and Murray Daw implemented this in their Molecular Dynamics (MD) code DYNAMO. The format they used to tabulate the EAM potential values to be read into DYNAMO has been taken as a standard by other programs like LAMMPS and ParaDyn. Hence it is helpful to know the format of the EAM potential files if you want to create an EAM potential file for a new material.

The computational materials science website at ASU is an excellent reference for EAM potential file format. I found it most helpful. You may ask why I am repeating the file format if it is available at ASU's website. Well, I had to dig deeper by evaluating the forces produced by the EAM potential in order to fully understand the EAM potential file format. I have a few points to add to the formats mentioned above that I hope will be helpful for those of you who are creating your own EAM potential files.

There are two types of EAM potential files; "setfl" (multi-element potential file) and "funcfl" (single element potential file). Since the format is succintly documented in ASU's website, I will just fill in the gaps which I think are useful.

Embedding function, Electron density & Pair potential

The values of the embedding function, electron density and pair potential are written from left to right in a row just like typing (not in a column). I do not know the reason for this processing. I suspect this may have something to do with old legacy systems where you did not want to waste the columns available in each row.

Hence to get the values you have to read left to right in a row as illustrated below.

EAM data format.

Pair Potential

The pair potential in the EAM file is in different formats for "funcfl" and "setfl" files.

  • In funcl files, it is written as sqrt(r*phi(r)).
  • Setfl files have it written as r*phi(r).

Hence the values go from r = 0 to r = rcut-dr. (This is how LAMMPS will assume the values are written.)

* NOTE: dr should always be rcut/nr.

Multi-element "Setfl" format

  • After the embedding funtion (line 7) the electron density is written (which is missing in the above) followed by the second element and this repeats.
  • In case you are wondering how the pair potentials are ordered if there are 3 elements, here is the format:
    • pair potential for type 1 & type 1
    • pair potential for type 2 & type 1
    • pair potential for type 2 & type 2
    • pair potential for type 3 & type 1
    • pair potential for type 3 & type 2
    • pair potential for type 3 & type 3
      • Note that this is the format that LAMMPS uses and it would be wise to check with the particular code you are using to be sure!
readEAM: A matlab code for reading EAM files can be downloaded here.

References

[1] Daw, M.S. and Baskes, M. I. "Embedded atom method: Derivation and application to impurities, surfaces and other defects in metals", Physical Review B 29, 6443-6543 (1984).
[2] Finnis, M. "Interatomic forces in condensed matter", Oxford series on materials modeling, Oxford University press, 2003.

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