Hi all,

I tried to run a MD simulation modeling a slab of liquid which contains a few charged atoms (the charges equal -1 or 1) on top of a solid charged surface (1% of the solid atoms are charged). I use the lj/cut/coul/long pair_style together with the PPPM option. I have periodic boundary condition in the x and y direction but not in the z direction (reflecting wall). I use use the kspace_modify slab 3.0 option

When the default value of the dielectric constant (1.0) is chosen, the simulation runs well with the PPPM initialisation giving:

G vector = 0.0965039

grid = 15 15 60

RMS precision = 5.61492*10-5

buck FFT buffer size/proc = 24800 13500 11160

So far, so good.

As I would like to model water at ambient temperature, I then fix the dielectric constant to 80.0 and launch the simulation.

I get the followig error message: PPPM stencil extends too far, reduce PPPM order.

Therefore, I add, in the input script, the line:

kspace_modify order 1

but it does not change the error message.

I then change the previous line by

kspace_modify mesh 15 15 60 order 1 gewald 0.0965 to mimic the values given by the PPPM initialisation when the dielectric constant equals 1.0

The simulation starts but crashed after somes steps. The error message is "Out of range atoms - cannot compute PPPM"

Do you have an idea of a way to make this simulation runs ?

Thank you ahead

PS: I join the input script.

DataSalt.inp (3.07 KB)