[lammps-users] Fcc lattice

hello all,

I am trying to create a block of dimensions 250250500 A and fill it with fcc lattice. I try to create groups of atoms by defining a layer of atoms on the top (+z) and the bottom (-z). My problem is that the number of atoms in the bottom layer is double that in the top layer, though these layers are of same dimensions. A simple calculation using the ratio of volume of the layer to that of a fcc unit cell shows that the number on the top layer is correct. I am attaching the input script.

Can anyone point out the mistake i am making?

Thanks in advance,

in.test (721 Bytes)

I'd play with and viz a smaller sample until
you see what the various commands are doing.