meam/ all pair coeffs are not set

Dear LAMMPS users,

I’m new LAMMPS user. I am attempting to model the interface between a titanium carbide thin film and a Ti6Al4V substrate but I’m having trouble with the input file. The objective is to essentially do a pull-off experiment in LAMMPS where I remove the thin film from the substrate. I’ve shared a link to my project files. Inside you’ll find:

  1. A dump file from when I got the program to run but incorrectly

  2. A meam library file

3)The input file

  1. 2 meam parameter files for TiAl and TiC

  2. An lmp file giving the coordinates of the atoms

The specific lines in the input file that are giving me trouble at the moment are:

potentials

pair_style hybrid meam/c morse 2.5

pair_coeff * * meam/c library3.meam Al NULL NULL Al NULL

pair_coeff * * meam/c library3.meam Ti NULL Ti NULL NULL

pair_coeff * * meam/c library3.meam C NULL NULL NULL C

pair_coeff * * meam/c library3.meam Ti Al TiAlpar2.meam Ti Al NULL

pair_coeff * * meam/c library3.meam Ti C TiCpar2.meam Ti NULL C

pair_coeff 2 3 morse 0.4691 1.738 2.246

the error says: All pair coeffs are not set

Project files:

https://drive.google.com/open?id=1NQZ7SzK3MjxwS8Kc9jHY7Iv0ZQIJHs6u

Best Regards,

Nathanael

Dear LAMMPS users,

[…]

The specific lines in the input file that are giving me trouble at the moment are:

potentials

pair_style hybrid meam/c morse 2.5

pair_coeff * * meam/c library3.meam Al NULL NULL Al NULL

pair_coeff * * meam/c library3.meam Ti NULL Ti NULL NULL

pair_coeff * * meam/c library3.meam C NULL NULL NULL C

pair_coeff * * meam/c library3.meam Ti Al TiAlpar2.meam Ti Al NULL

pair_coeff * * meam/c library3.meam Ti C TiCpar2.meam Ti NULL C

this is all very wrong for two reasons:

  • because of the ‘* *’ form, each pair_coeff command will effectively wipe out the previous one.
  • furthermore, MEAM is not a pairwise additive potential. You are missing important contributions if you break it down the way you do.
    thus you a) should not use pair style hybrid and b) you should have one pair_coeff * * library3.meam Ti Al C combined.meam Ti Al C
    and you have to properly combine the contents of TiAlpar2.meam and TiCpar2.meam. This is quite tricky and thus you need to read the documentation of pair style meam/c VERY carefully.

axel.