Write_data lammps does not update the velocities

LAMMPS
1

Dear All,

I am currently simulating polymer systems using LAMMPS (as of 17th February 2022). The simulations are conducted using Berendsen thermostat and NVE time integration to update the velocities.

I have employed the following commands:
fix 1 all temp/berendsen 400.0 400.0 100.0
fix 2 nve

During the simulations, the temperature is maintained at 400K+/-2K (with some fluctuations), and the simulations run successfully. The results obtained are fine to me. However, I encountered a problem while writing the data file at the end of the simulation using the ‘write_data’ command. The velocities recorded in my output data file are the same as the input data file. Is this correct? or should the velocities have been updated?

Thank you,

2

It is impossible to verify what you claim that happens. You need to provide the input and data files (before and after) to prove your point.

3

If that’s the case, then you used something like:

write_data myfile.data
run 50000

instead of:

run 50000
write_data myfile.data