Question about cutoff for pair style eam/alloy

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1

Hello,

I have a question about how cutoffs are handled when using the pair style eam/alloy.
With this style you specifc the cut off within the DYANMO file for the potential.
I was wondering if there was any sort of smoothing that is used, or if its just a hard cut off.
I checked the documentation and it doesn’t seem to be very specific.

Thank you,
Joseph Vella
PhD Candidate
Department of Chemical And Biological Engineering
Princeton University

2

All the tabulated EAM functions in an EAM file go to 0.0 smoothly
at the cutoff. “Smooth” means the derivatives as well, which
EAM encodes as cubic splines, so the splining is also “smooth”.

Steve

3

Thank you Steve.
Just a quick clarifying question.

Hypothetically if I take a cut off distance before the pair potential is close to zero, the EAM code will ensure that it goes to zero smoothly using cubic splines?

Sorry if this was obvious in your last email, I just want to make sure I understand correctly.

Thank you again,

Joseph Vella
PhD Candidate
Department of Chemical And Biological Engineering
Princeton University

4

no, that’s not right. The cutoff is in the EAM potential file.
The tabulated functions in that file all use the cutoff. If
you changed the cutoff in the file, you’d have to also

change the tabulated values to go to zero at the new cutoff.

Bad idea, since the potential is parameterized for the material
and that includes choice of cutoff.

The splining in LAMMPS simply uses the tabulated values
from the file to fit to.

Steve