[lammps-users] FW: Problem: Atomic position out-of-control

I'm not sure what you're asking. The data file doesn't list I,J pair
interactions
where I != J. Those will be mixed according to the default rules. If you
want to override the default, then you need to do that in your input script.
But it doesn't look like you are.

Steve

Hi, Steve:

It might be the point. In the input, I defined buck coefficient I != J case explicitly (as below) in the input script, while it doesn’t seems effective from reading the data output (see below), as the case I != J was not peresented. The data output was creeated via restart2data command. Do you think my input of pair_coeff correct? How to override the defaut mixing rule for the case I != J?

input:

Atom type 1,2 for Mn atoms & 3,4 for O atoms

Forcefield

pair_style buck 6.0
pair_coeff 1 3 23230.644 0.3299 0 # Mn-O interaction
pair_coeff 1 4 23230.644 0.3299 0
pair_coeff 2 3 23230.644 0.3299 0
pair_coeff 2 4 23230.644 0.3299 0
pair_coeff 3 3 220175.958 0.21916 737.92 # O-O interaction
pair_coeff 3 4 220175.958 0.21916 737.92
pair_coeff 4 4 220175.958 0.21916 737.92
#zero
pair_coeff 1 1 0 0.2 0 # Mn-Mn interaction
pair_coeff 1 2 0 0.2 0
pair_coeff 2 2 0 0.2 0

Output data file:

6050 atoms
4 atom types
0 50 xlo xhi
0 50 ylo yhi
0 111.12 zlo zhi
Masses
1 54.938
2 54.938
3 15.999
4 15.999
Pair Coeffs
1 0 0.2 0
2 0 0.2 0
3 220176 0.21916 737.92 ------ # didn’t show the case for I!=J.
4 220176 0.21916 737.92
Atoms

Please read the doc page for pair_style buck. It says:

None of the Buckingham pair styles support mixing. Thus, coefficients
for all I,J pairs must be specified explicitly.

So your input script will need to define the I,J coeffs when I != J.
This is true whether you are running for the first time, or reading
a data file created from a restart file. If you read the restart
file directly, then I think you don't need to do this in your
input script.

Steve