[lammps-users] Fix deposit and initial velocity

Lammps Users,

I am depositing atoms onto a Lennard-Jones 9-3 wall using fix deposit. I find that if the deposit region is outside the Lennard-Jones wall cutoff, the new particles do not move, even if I provide them with initial velocities as following:

fix 2 addatoms deposit 500 1 5000 234235 region slab near 3.0 vz -1.0 -0.8 units box

Interestingly, when I remove the velocity component of the fix deposit (vz -1.0 -0.8), the system evolves through interactions between the atoms, something it does not do when the initial velocities are added. Any help would be appreciated.

Thank you,
Noah Kastelowitz

I assume you are adding the atoms to a group that you are time integrating?
Have you dumped the velocity of the new atoms, to see what values
they have?



Yes, the atoms are being added to the group being time integrated. I checked the velocities of the deposited particles when vz -1.0 -0.8 is included in the fix deposit, they are zero. I’ve attached my input and potential if it’s helpful.

Thank you,

mW.sw (500 Bytes)

in.deposit (1.08 KB)

In your script you appear to be thermostatting the atoms
you are adding via NVT in some way I don't quite understand.

I would test this initially with no thermostatting, just run NVE,
and see if your ad-atoms have the velocity you expect. If they
do, then your thermostatting procedure is messing things up.