pair_stype hybrid of two eam potential files

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1

Dear LAMMPS-users:

I have a model containing two blocks, one is CoPt, and the other is AlO. Besides the streitz potential for AlO, I am applying one eam file for AlO & another eam file for CoPt. with script below:

pair_style hybrid/overlay coul/streitz 12.0 wolf 0.2 eam/alloy

pair_coeff * * coul/streitz AlO.streitz NULL NULL Al O

pair_coeff * * eam/alloy AlO.eam.alloy NULL NULL Al O

pair_coeff * * eam/alloy CoPt.eam.alloy Co Pt NULL NULL

However, it shows an error an “All pair coeffs are not set”. I guess might be the reason of no parameters between AlO and CoPt blocks. However, I am not intend to use EAM for such inter-block interactions.

Therefore, my questions is

  1. Is there a way to use different EAM potentials for ALO & CoPt blocks individually, but no parameters for interactions between AlO and CoPt?

  2. Or, I have to combine all the four atom types into one eam file?

Thanks & Best Rgds!

Dai Ling

2

Dear LAMMPS-users:

I have a model containing two blocks, one is CoPt, and the other is AlO.
Besides the streitz potential for AlO, I am applying one eam file for AlO &
another eam file for CoPt. with script below:

pair_style hybrid/overlay coul/streitz 12.0 wolf 0.2 eam/alloy

pair_coeff * * coul/streitz AlO.streitz NULL NULL Al O

pair_coeff * * eam/alloy AlO.eam.alloy NULL NULL Al O

pair_coeff * * eam/alloy CoPt.eam.alloy Co Pt NULL NULL

However, it shows an error an “All pair coeffs are not set”. I guess might
be the reason of no parameters between AlO and CoPt blocks. However, I am
not intend to use EAM for such inter-block interactions.

well, how should those atoms then interact, if at all? you will have
to tell LAMMPS how they are supposed to interact (using sub-style
none, if not at all).

mind you, there is another problem with this input. your second
"pair_coeff * * eam/alloy" alloy line will wipe out the previous one.
please look up in the pair hybrid documentation how to specify two
different manybody potential files.

Therefore, my questions is

1) Is there a way to use different EAM potentials for ALO & CoPt blocks
individually, but no parameters for interactions between AlO and CoPt?

yes. please read the documentation for pair style hybrid *very*
carefully. all you need to know is there. but note, that what you are
trying to do is very complex, so you should construct test cases to
test against non hybrid pair style setting, that each segment works.

2) Or, I have to combine all the four atom types into one eam file?

no, but be aware, that when turning off interactions, there are not
going to be any forces between those atoms, i.e. they could move
through each other.

axel.