Write_data lammps does not update the velocities

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,

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.

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

write_data myfile.data
run 50000

instead of:

run 50000
write_data myfile.data