[lammps-users] Question about stress output from thermo_style

Dear LAMMPS users

I try to use LAMMPS calculate the elastic constants of silicon based on some potential. I use to following command:

fix 2 all deform 1 yz erate 2

thermo_style custom step yz pyz

to deform the simulation box. But the output is as follows:

0 0 0.011967162
1 0.01881008 0.011967162
2 0.037620159 -1230.7087
3 0.056430239 -2457.9835

While it began to have linear elastic behavior for step 2 and step 3, the stress in step is 0.

It seems like the stress output is one step before the simulation step, for example when yz = 0.0188, pyz = 0. But when yz = 0.03762, pyz = -1230.7087. Then yz increase by 0.0188 to 0.05643, the stress increase by -1230.

Thanks very much for your help!


How are you running the simulation?
Why do you think the stress is (or should be) zero for yz = 0.
The output says it is not. That would presumably be the case
even if you didn’t use the fix deform command.