Creating two alloys within a single simulation box

LAMMPS LAMMPS General Discussion
1

Hi Guys,
I wanted to define two alloy (using a singe potential) in my simulation box,
I tried this but it seems not working. The problem is that I cannot see the defined compositions in the two defined regions !

Could you please tell me how to solve it!
Thanks

------------Initialization ------------

units metal
dimension 3
boundary p p p
atom_style atomic
variable latparam equal 3.595

Define simulation box

lattice fcc ${latparam} orient x 1 0 0 orient y 0 1 0 orient z 0 0 1
region simbox block 0 20 0 20 0 20
create_box 4 simbox

------------ First alloy Definition ------------

region X block 0 20 0 20 0 10
create_atoms 1 region bom

mass 1 55.845 # Fe
mass 2 58.69 #Ni
mass 3 51.996 # Cr
mass 4 2.01 #H

set type 1 type/fraction 2 0.05 543
set type 1 type/fraction 3 0.015 111
set type 1 type/fraction 4 0.0 123

------------ Second alloy Definition ------------

region Y block 0 20 0 20 10.1 20
create_atoms 1 region pox

set type 1 type/fraction 2 0.6 543
set type 1 type/fraction 3 0.12 111
set type 1 type/fraction 4 0.0 123

2

Note that the regions bom and pox were never defined, but I am going to suppose that you are refering to the regions X and Y.

Your problem is that, here, both create_atoms commands are creating only atoms of type 1, and each set command applies to all atom of type 1, and not just the atoms of type 1 from the last defined region.

Simon

3

Why don’t you just use different atom types for each region? 1-4 for the first and 5-8 for the second? No more clashes; problem solved.

4

Thank you Simon and Akohlmey.

Akohlmey, your solution worked !

Just one more question.
Is it possible to define the two alloys in two different simulation boxes rather than one single box?

5

Yes and no.

There can be only one box at a time, so you would have to do two simulations one after the other. Or use LAMMPS’ multi-partition feature to run two different simulations concurrently.

1 Like