Defining interstitial sites for C in Fe lattice

LAMMPS LAMMPS General Discussion
1

Hi,

When defining an alloy in LAMMPS, for example Fe-2%Ni, we typically first define the structure for Fe and then assign 2% of the Fe atoms to Ni using the following commands:

set type 1 type/fraction 2 0.02 543

This replaces 2% of the Fe atoms with Ni in a substitutional manner. But how do we handle interstitials, such as carbon in Fe? If I use the same code for carbon, it will place C atoms in substitutional sites like Ni, but I need them to occupy interstitial sites.

I’ve been using the following code:

units metal
atom_style atomic
boundary p p p
atom_modify sort 0 0.0

variable a equal 2.86365733518054
lattice bcc $a
region box block 0 10 0 10 0 10
create_box 2 box
create_atoms 1 box
create_atoms 2 single 0.5 0 0.5

This only creates a single interstitial C atom. How can I modify this to place, say, 1000 interstitial C atoms?

If I use “random” command it will not go interstitial !
I should use “single” so that I can specify the coordination (i.e. .05 0 0.5)

Thanks

2

LAMMPS has no knowledge of and no way to classify those positions, so it cannot be done from inside LAMMPS.

You need to look for suitable tools outside of LAMMPS or write one yourself that works for your specific system of interest.

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3

If interstitials create some kind of lattice, you can define it via lattice custom, create the atoms and then randomly delete some of them.

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