dump unwrap, coordinate limit

Hi All,

I have fluid inside a pore and I’m applying external force on the fluid to simulate Poiseuille flow. I dump the coordinates of the fluid with dump_modify unwrap yes option. Initially the fluid CM is at zero and with time it moves in the filed direction. I’m running a very long simulations. After the fluid CM reaches around 250~nm, the fluid suddenly renter from the other side of the box with CM around -250~nm. Its like as if the system dimensions in field direction are from around -250 to 250~nm. The actual pore dimentions in the filed directions are from -2 to 2~nm only.

Is there a restriction on dump modify unwrap or the (maximum) coordinate values lammps can have ?

With regards,
Alan Sam

Is there a restriction on dump modify unwrap

yes, there is a limit on how big a periodic image can be stored - it’s 512 (in a dimension) by

default. If you compile with -DLAMMPS_BIG_BIG its 1 million. Search

the Section_start.html doc page for BIGBIG to see the details, since it

has to do with how you build LAMMPS.