How to create FCC [111] plane and use of "orient"

LAMMPS LAMMPS Beginners
1

Hi everyone,

I want to create an FCC lattice along the [111] plane. I’ve used the following input script. However, I want to know if the “lattice fcc” command in LAMMPS generates the lattice along the [111] plane by default. If not, what plane does it create, and what should I write to get the lattice along the [111] plane? I’ve seen something with the keyword “orient,” but I’m not sure exactly what it does.

Thanks
TP

units lj
atom_style full
boundary p p p
lattice fcc 0.8
region box block 0 13 0 13 0 1.8
create_box 1 box
create_atoms 1 region box

2

You can easily find out the answers to your questions by writing out the system geometry with write_data or write_dump and then visualize the result with your favorite visualization tool. Or use the built in visualization of LAMMPS (dump image).

3

By using “lattice fcc 1.0 orient x 1 1 1 orient y 1 -1 0 orient z 1 1 -2” I can create close-packed hexagonal structure along x-y plane, but if I want to have the [111] plane along z-direction, what should I write? Also, I tried

a) orient x 1 -1 0 orient y 1 1 -2 orient z 1 1 1 (didn’t work, no periodic structure)
b) orient x 1 -1 1 orient y -1 1 1 orient z 1 1 1
ERROR: Lattice orient vectors are not orthogonal (src/lattice.cpp:232)
Last command: lattice fcc 1.0 orient x 1 -1 1 orient y -1 1 1 orient z 1 1 1

Note lattice fcc 1.0, here 1.0 is reduced density as I am using units “lj”

Thanks. Looking forward for suggestions
TP

4

If you are using a lattice orientation other than the default 1 0 0 orientation, you may need to use a box with dimensions that are integer multiples of the lattice spacing to have seamless continuation across the periodic boundaries. Which multiples are needed is for you to figure out. Please have a look at a text book on crystallography if you need more detailed information.

5

It is also possible to define a custom lattice, consisting of orthogonal lattice vectors, in order to satisfy periodic boundary conditions. In case you need to have (111) plane along z-axis, there would be 6 atoms in a basis set.

variable a1 equal 1/sqrt(2)
variable a2 equal sqrt(6)/2
variable a3 equal sqrt(3)

variable a equal 3.615
lattice custom ${a} &
a1 ${a1} 0.0 0.0 a2 0.0 ${a2} 0.0 a3 0.0 0.0 ${a3} &
basis 0 0 0 &
basis 0.5 0.5 0 &
basis 0 0.3333 0.3333 &
basis 0.5 0.8333 0.3333 &
basis 0.5 0.1666 0.6666 &
basis 0 0.6666 0.6666

With this lattice, it is more convenient to define region boundaries.