question about changing units

Dear LAMMPS users and developers:
I’m confused about units command in lammps.
I used mirco units and I got good results. But when I changed to si units and I did not change the input data, I got wrong results, I mean different trajectories. I noted that the timestep 0, these two cases have the identical force output.
In my view, changing units command will not change the trajectories and all output generated by the simulation, what’s wrong?
ps: I use NVT ensemble.

Dear LAMMPS users and developers:
I’m confused about units command in lammps.
I used mirco units and I got good results. But when I changed to si units and I did not change the input data, I got wrong results, I mean different trajectories. I noted that the timestep 0, these two cases have the identical force output.
In my view, changing units command will not change the trajectories and all output generated by the simulation, what’s wrong?

your view is wrong. changing the units will change the units of your simulation parameters and thus it must change your results when their relative size changes. e.g. compare the mass unit vs. time unit for si and micro. the fact that you get identical forces only shows that some of your units have the same change between the different choices, but only when all would have the same scaling factor, should your results be unchanged.

axel.

axel.

I still don’t understand. We input figures and solver output figures, solvers can not help us change the figures. We use consistent units and we get the right answer. What exactly the command units do?Only remind us we are using units si, micro, metal…?

在 2020-01-13 12:10:46,“Axel Kohlmeyer” <[email protected]…24…> 写道:

What the units command does is explained in the manual and that is quite detailed.
Axel