error: Non-numeric atom coords - simulation unstable (../domain.cpp:521)

Hello LAMMPS community,

I’m running a simple test for SPC/E water, a fairly trivial model, with geometry generated from MolTemplate, using equidistant spacing 3.45A between molecules. After setting up the geometry, I then run the nve + Langevin with 1K, and ‘kspace_style pppm 0.0001’ to perturb the geometry, before equilibrating the simulation cell.

Attached is the screenshot from VMD visualization, with periodic boundary condition. However, it returns with error:

Step Temp E_pair E_mol TotEng Press
0 0 3.1403491e+17 0 3.1403491e+17 -nan

and

ERROR on proc 2: Non-numeric atom coords - simulation unstable (…/domain.cpp:521)

I’ve also checked the units, and they seem correct. Units ‘real’ was used. I couldn’t see anything wrong with the setup. Would you please tell me what could have gone wrong for this simple simulation?

Many thanks,
Anh Tran

Screenshot from 2016-11-21 17-49-39.png

Probably you have atoms sitting on top of each other, r_ij=0, which generates non-numeric forces. This could be due to two copies of an atom being created at a periodic boundary.

Aidan