[lammps-users] Restrictions on the form of EAM-type potentials?

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1

Dear all,

I have a question about EAM-type potentials that can be used with LAMMPS.

A pair potential function f(r) is tabulated in the DYNAMO86 format as
sqrt(r*f(r)), i.e. as an effective charge (and only in this way to my
knowledge). This fact restricts f(r) to be always a non-negative function.
Nowadays it is not the case for many EAM-type potentials.

An obvious solution might be to make use of the EAM potential transformation
like f(r) -> f(r)+2g*rho(r) in order to remove negative values from f(r).

However there exist EAM models that have charge density rho(r)=0 in the range
where f(r)<0. And this method fails. I wonder if such potentials can be used
with LAMMPS? Or it is necessary to modify its source code?

Thank you.

Vladimir

2

Here is Stephen Foiles answer:

Vladimir,

There are two file formats that are used with both dynamo and LAMMPS. The
comments that you make refer to the ‘funcfl’ file format in dynamo. There
is another file format, ‘setfl’, that avoids the issue that you raise. In
that case, the file contains r*phi® where phi® is the pair potential. If
you need more information, let me know.

Stephen Foiles