Hi,
I’m simulating an organic compound. I had defined a force field for the organic system via pair_style, bond_style, angle_style, dihedral_style and improper_style, in other words, I had defined a set of force field parameters in a data file. At the beginning of the simulation, I observed something not right.
In my data file, I defined :
Bonds
#(id) (type) (atom_id) (atom_id)
…
17 7 21 1
18 8 1 2
19 8 1 6
…
Observe that atom with id=1 has at least 3 bonds. However, at the beginning of the simulation, LAMMPS says
2 = max bonds/atom
This is not correct, and I’m afraid this might affect the outcome. I wonder can we set the max bonds/atom? or Is there any error in my data file, otherwise LAMMPS should set the max bonds/atom to be 3 or 4 by default.
Thank you for your time.
Cheers,
Christopher
hi christopher,
Hi,
I'm simulating an organic compound. I had defined a force field for the
organic system via pair_style, bond_style, angle_style, dihedral_style and
improper_style, in other words, I had defined a set of force field
parameters in a data file. At the beginning of the simulation, I observed
something not right.
In my data file, I defined :
Bonds
#(id) (type) (atom_id) (atom_id)
...
17 7 21 1
18 8 1 2
19 8 1 6
...
Observe that atom with id=1 has at least 3 bonds. However, at the beginning
of the simulation, LAMMPS says
2 = max bonds/atom
This is not correct, and I'm afraid this might affect the outcome. I wonder
actually, it is very likely to be correct. you have to consider that LAMMPS
by default tries to apply newton's third law. i.e. it will compute the forces
from a bond only once. the first bond is going to be accounted with atom 21,
whereas the other two bonds will be accounted with atom 1.
this would be different, if you disable using newton's third law for bond
calculations. you can look it up in the read_data.cpp file around line 1070
can we set the max bonds/atom? or Is there any error in my data file,
otherwise LAMMPS should set the max bonds/atom to be 3 or 4 by default.
no this should be ok as is. the output is a bit sloppily worded.
if it would say bond force calculations per atom, it would
be more correct, but perhaps equally confusing.
cheers,
axel.