[lammps-users] body_style sphere with pair_style lj

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1

Hello,

I’m looking at the rigid body box simulation (https://github.com/lammps/lammps/blob/ce79622897681e235247b53b3e297bcb3ca9c1ba/examples/ASPHERE/box/in.box) that uses “body_style sphere” and the “pair_style lj”.

How does the pair potential calculate the pair distance since in the example, the particle has a radius? Is it from the center of the sphere?

In this case, what would be the point of using a spherical particle vs. a point particle (besides being a simple example)?

Thanks,
Stacey

2

a) you should be talking about “atom_style”, not “body_style”
b) the radius and torque properties provided by atom_style sphere are required by the use of fix srd in that example
c) the torque caused by the SRD particles on the “big” particles will be applied to their motion due to using fix rigid.

3

Thanks Axel

My bad on the atom_style.

How is the pair potential calculated between the spherical particles since they have a radius? If the distance is calculated from the center of each particle, then the LJ sigma would need to be chosen to not have strong particle-particle overlap.

Thanks again!

4

neither of the pair styles (soft or lj/cut) pays any attention to the radius property. for those you provide an “effective radius” through the pair_coeff settings.
the radius property is only accessed by fix srd and the torque property by fix srd and fix rigid.