Potentials for Mgo in nanoindentation

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1

Dear all,

I hope this email finds you well.

Now I am using LAMMPS to simulate a 3D nanoindentation into MgO with the buck/coul/long potential. However it does not work. Part of the LAMMPS code is shown below.

pair_style buck/coul/long

pair_coeff 1 2 buck/coul/long 2143.768 0.26734 0.0 12.0

pair_coeff 2 2 buck/coul/long 25.31 0.6937 32.32 16.0

pair_coeff 1 1 buck/coul/long 0.0 1.0 0.0 12.0

kspace_style pppm 1.0e-4

Then, the buck/coul/long and the morse potential are combined to simulate the nanoindentation process. The results shows that many atoms are lost from the box. If the ij/cut potential was used in the place of the morse potential, the same error appears. Part of the LAMMPS code is shown below.

pair_style hybrid/overlay buck/coul/long 12.0 morse 5.0

pair_coeff 1 2 buck/coul/long 2143.768 0.26734 0.0 12.0

pair_coeff 2 2 buck/coul/long 25.31 0.6937 32.32 16.0

pair_coeff 1 1 buck/coul/long 0.0 1.0 0.0 12.0

pair_coeff 1 1 morse 0.0 0.0 2.0 5.0

pair_coeff 2 2 morse 0.0001 20 1.7792

pair_coeff 1 2 morse 0.0002 20 1.3136

kspace_style pppm 1.0e-4

I do a literature research and find that there are so few works focusing on the simulation of MgO using LAMMPS. So, could you give me some advice on how to select potential styles and the corresponding parameters for the nanoindentation simulation of MgO? Thanks a lot.

Regards,

Leiting Li

School of Civil Engineering, the University of Sydney.

2

Atoms lost from the box likely indicates a problem with your input rather than a problem with the code. Check your timestep size and check for overlapping atoms or incorrect pair style parameters.

Paul

3

Dear all,

I hope this email finds you well.

Now I am using LAMMPS to simulate a 3D nanoindentation into MgO with the
buck/coul/long potential. However it does not work. Part of the LAMMPS code
is shown below.

pair_style buck/coul/long

pair_coeff 1 2 buck/coul/long 2143.768 0.26734 0.0 12.0

pair_coeff 2 2 buck/coul/long 25.31 0.6937 32.32 16.0

pair_coeff 1 1 buck/coul/long 0.0 1.0 0.0 12.0

kspace_style pppm 1.0e-4

Then, the buck/coul/long and the morse potential are combined to simulate
the nanoindentation process. The results shows that many atoms are lost from
the box. If the ij/cut potential was used in the place of the morse
potential, the same error appears. Part of the LAMMPS code is shown below.

pair_style hybrid/overlay buck/coul/long 12.0 morse 5.0

pair_coeff 1 2 buck/coul/long 2143.768 0.26734 0.0 12.0

pair_coeff 2 2 buck/coul/long 25.31 0.6937 32.32 16.0

pair_coeff 1 1 buck/coul/long 0.0 1.0 0.0 12.0

pair_coeff 1 1 morse 0.0 0.0 2.0 5.0

pair_coeff 2 2 morse 0.0001 20 1.7792

pair_coeff 1 2 morse 0.0002 20 1.3136

kspace_style pppm 1.0e-4

I do a literature research and find that there are so few works focusing on
the simulation of MgO using LAMMPS. So, could you give me some advice on how
to select potential styles and the corresponding parameters for the
nanoindentation simulation of MgO? Thanks a lot.

from your input it is not clear what you are trying to do. what is
indenting what and how?
all i see is that you are adding two potentials on top of each other
and that is likely to give your problems.

you have to be more specific in your description and provide a
complete runnable minimal input deck.

axel.

4

Based on your description of the problem, you have probably skipped an
essential step: test the potential. This should be done before you
attempt anything complicated like nanoindentation. Testing could
include many things. For example:

1. simulate bulk crystal
2. simulate surface
3. simulate nanoindenter material in equilibrium with surface

Aidan

5

Dear Axel,

Thanks for your email and kind help.

Attached please find the complete input file and the pbs script. The parameters for the buck/coul/long potential are obtained from an open paper (J.D. Gale, Empirical potential derivation for ionic materials.Philosophical magazine B,1996,73(1):3-19).
I am a rookie for using the LAMMPS and it seems it is not easy to find a proper pair style and the corresponding parameters for the ionic materials like MgO. It is better if you can help me compile the input file. I appreciate.

Dear Paul and Aidan, could you please give me further help? The input file and the pbs script have been attached.

Thanks a lot.

Regards,

Leiting

pbs.v40 (937 Bytes)

creatmgostr.in (3.26 KB)

Empirical potential derivation for ionic materials.pdf (1.08 MB)

6

We can devote much time to any one user, so you should learn how to be
self-sufficient, or else find a person local to you who knows LAMMPS.
The key to learning how to use LAMMPS is to start with a simple
example and then add to it. There is nothing special about your MgO
simulation. You just need to read the relevant documentation and pay
attention to the results. Making comparison with published results is
an important way to make sure you are not generating random numbers.

Aidan