[lammps-users] On Hybrid potentials (Tersoff and EAM)

Hi Steve,

I am using the hybrid command to use tersoff and eam potentials for a simulation.

I have 4 types of atoms - l want tersoff potential for atom 2-2 (C-C) interaction, and eam for other interactions (1-1, 1-2, 1-3, 1-4 etc)
There are Cu and C atoms and carbon atoms are type 2

The input file is like below:

units metal
boundary f f s
atom_style atomic
pair_style hybrid tersoff eam

read_data data.cu_C

pair_coeff . tersoff SiC.tersoff NULL C NULL NULL

pair_coeff 1 * eam Cu_u3.eam
pair_coeff 2 3 eam Cu_u3.eam
pair_coeff 2 4 eam Cu_u3.eam
pair_coeff 3 3 eam Cu_u3.eam
pair_coeff 3 4 eam Cu_u3.eam
pair_coeff 4 4 eam Cu_u3.eam

I got an error: incorrect args for pair coefficients

Please, what could be wrong?




That’s not the way EAM is designed to be used. Physically, you
are wanting to model Cu-C interactions with a Cu EAM potential,
which makes little sense. Conceptually, you need to define
certain atom types as Cu, then define EAM interactions between
the I-I and I-J interactions within that set of types.

So in your example it would make more sense to have the
2-2 interaction = Tersoff
and if types 1,3,4 = Cu, then define all the combinations of 1,3,4 as
Cu EAM. Then define some other interaction (e.g. LJ) between
type 2 atoms and type 1,3,4 interactions.