Issue related to the Al-Cu bond order potential

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1

Dear LAMMPS Users,

I am working on the Al2Cu-Al eutectic structure and using the Al-Cu bop potential file available in the LAMMPS potentials directory.

I found that the pressure found from the stress tensor and the pressure directly calculated from the LAMMPS are not matching, which is supposed to match according to the manual ( https://lammps.sandia.gov/doc/compute_stress_atom.html ). I have verified that it matches for other potential.

I have given here a sample LAMMPS input script and data file.

data.al2cu_sample.lmp (357 KB)

2

How big is your system size? BOO requires a minimum size. I would try a size that is four times cutoff just to see what happens.

Xiaowang

3

Dear Zhou,

I have verified the issue for very bigger size system, about the size of 10 nm x 10 nm x 10 nm.

Thanks,
Mathiazhagan S

4

please note, that pressure for shrinkwrap boundaries has no meaning. your volume is infinitely large and thus pressure is always zero. LAMMPS will use the actual volume of the simulation box, but that cannot be accurate in this case. please use periodic boundaries.

axel.

5

Dear Axel,

I verified for both the periodic and non-periodic cases.

I used the shrink-wrap boundary condition, mainly because it was difficult to make periodicity for both the Aluminum and Al2Cu phases (for the crystal structure and orientation considered).

Moreover, I found the issue during the equilibration, before the pressure tends to reach the value of zero.

Thanks,
Mathiazhagan S