error cpp

I work with ionic liquid([BMIM][PF6]), I use pair_style
lj/cut/coul/long command ,and the length of simulation box is 170,and
cutoff 12, and timestep 1,neighbour 2.0 bin,neigh_modify delay 0 every
1 check yes,kspace_style pppm 1.0e-4,units real,
I recive this error after 80000th step: "Out of range atoms - cannot
compute PPPM"
can you help me to solve this error

Please read the manual on this error in doc/Section_errors.html.
It gives several ideas why this happens - typically b/c of bad