[lammps-users] Help

Hi lammps user,
I am performing lammps simulation, and I prepared my data file from material studio and then import it to lammps using msi2lmp.exe tool provided with lammps. I am using hybrid potential (Tersoff and PCFF) for my simulation. The simulation runs well without any error but when I implement NPT ensemble, the density is supposed to converge but it’s not converging. Does anyone help me with what wrong is happening with my simulations? The input file and log files are attached with this mail.

min.txt (18 KB)

1.1.in (4.27 KB)

5_5BNNC60.11.rar (363 KB)

From your input file it can be seen that the damping parameters you set will make both the temperature and pressure converging almost impossible:

  fix 1 all npt temp 100.0 100.0 100.0 z 1.0 1.0 1000.0
I would suggest changing this line to

  fix 1 all npt temp 100.0 100.0 0.01 z 1.0 1.0 0.01

But keep playing around with Pdamp and Tdamp until you get the stability you need. I'd suggest keeping those values between 0.01 and 1


values between 0.01 and 1 are very wrong for real units. they are far too small.
please note that real units have femtoseconds as timestep and not picoseconds.

also, you have overlooking the bigger problem of requesting isotropic box scaling for a system that is definitely anisotropic.