Hi,
I am trying to use lammps with periodic boundary conditions for a system with x, y, and z directions oriented normal crystallographic directions [111] [-1-12] and [-110].
However, the atoms at the ends of the simulation box don't have a perfect coordination number. I tried for fcc metals and the coordination number is less than 12. It works fine if the orientations are [100].
Could anyone kindly suggest if there is anything wrong I am doing or if there is a way out of this problem.
Here is the part of the script that creates the box and the atoms:
dimension 3
boundary p p p
units metal
atom_style atomic
# create geometry
lattice fcc 3.615 origin 0.0 0.0 0.0 orient x -1 1 0 orient y -1 -1 2 orient z 1 1 1
region box block -30.32 30.32 -27.1 27.1 -3.5 3.5
create_box 1 box
create_atoms 1
Thanks in advance,
Kedarnath Kolluri
Unless your box size is a multiple of the lattice spacing
you won't get a periodic system. Your specified box
size is not in Angstroms, but in lattice spacings, so it's
not obvious to me that it is a multiple. Are you sure
you don't want to append "units box" to your region
command to get a box in Angstroms?
Steve
Thank you Steve,
I was trying to make sure the box size was an integer, and ignoring the need for it to be a multiple of lattice spacing.
However, I have another question. I am trying to deform the system by uniaxial or biaxial expansion and if I deform it using vol/rescale and the new deformed dimensions of the box are not multiple of lattice spacing, will I have the same problem at the edges of the supercell ? If so, should I always deform it such that the new box size is a multiple of original lattice spacing ?
Thank you,
Kedar.
Once you have a periodic system, you can deform it via volume
or box length changes however you wish, and it should stay
periodic.
Steve