Getting NAN output from fix npt command

The potential energy is way too high. Check your configuration again.

The potential energy is way too high. Check your configuration again.

actually, it is way too _low_.

but more importantly, you shouldn't need to use pair_style
hybrid/overlay for this kind of setup, but simply use pair_style
hybrid
however, with this change LAMMPS will complain about missing
parameters. also, your water model interactions are not consistent
with popular water models, so i would worry about this, too. finally,
at least one of the water molecule geometries is not properly entered;
it looks like the image flags for the oxygen are wrong, leading to
very long bonds.

axel.