I am aware that the lattice and the "region prism" to define the box are independent. However,

in many cases, you would like the simulation box to be an integer number of lattice unit cells.

The question that I have regarding the order of the tilt distances does concern what is written

in the LAMMPS doc pages.

For the the "region prism" command it says :

prism args = xlo xhi ylo yhi zlo zhi xy xz yz

In my particular case I wish to create a periodic simulation box that has precisely the dimensions of 10 lattice repeat vectors

in each of the 3 directions. The geometry of the lattice, containing 4 basis atoms, is defined by (a,b,c,90,beta,90). This means

that only the angle between the a (x) and c (z) axes is different from 90. This means that the only nonzero

tilt shift would be the xz. According to the order of the tilt displacements in the doc pages, xz should appear as

the second tilt shift. But if I put this number in the second place, the other two being zero, the number of atoms in the

region is NOT 4000, as it should. But if I put the tilt displacement xz in the first place, with the second and third equal to

zero, the region contains exactly 4000 atoms, as expected. Probably I�m doing something wrong, but I have not been able

to figure out what.

Steve Plimpton wrote: