Cant assign two boundary conditions at lower and upper faces in change box

Dear lammps users,

I am trying to change th p p p to ps p p conditions using change box but getting error
both sides of boundary must be periodic. Although it is written in change box doc that two conditions can be used for lower and upper face. Any idea why this happens?

thanks.
Rajesh

Dear lammps users,

I am trying to change th p p p to ps p p conditions using change box but
getting error
both sides of boundary must be periodic. Although it is written in change
box doc that two conditions can be used for lower and upper face. Any idea
why this happens?

‚Äčit happens because what you are asking for makes no sense at all.
when asking for periodic boundaries it is geometrically impossible to have
anything but periodic boundaries on *both* sides of the box.

axel.