Dear Axel and lammps-users

i am trying to occupy carbon atoms in my simulation box in the interstitial positions. but i am not sure what should i use in create_atoms command? is the random word the right one?

Thanks for your help.

Dear Axel and lammps-users

i am trying to occupy carbon atoms in my simulation box in the interstitial positions. but i am not sure what should i use in create_atoms command? is the random word the right one?

Thanks for your help.

random will give you an amorphous system, which is not what you want. If you have just a few interstitial atoms, you can enter them by hand by editing a data file or using create_atoms single. If you want to place a large number of interstitial atoms, I suggest the following.

- Identify the lattice structure that includes both the original lattice and the interstitial sites. For example, I believe that BCC Fe and octahedral interstitial sites together make a simple cubic lattice, with the Fe atoms lying on the even sites and insterstitials on the odd sites.
- Build a system with all sites occupied, in the manner that is described for Wurtzite in lattice.html. These instructions were mysteriously truncated, so I repeat them below.
- Delete the desired fraction of interstitial atoms using the delete_atoms porosity command

Aidan

Here are the complete commands for Wurtzite, now posted at lattice.html:

```
variable a equal 4.340330
variable b equal $a*sqrt(3.0)
variable c equal $a*sqrt(8.0/3.0)
```

```
variable 1_3 equal 1.0/3.0
variable 2_3 equal 2.0/3.0
variable 1_6 equal 1.0/6.0
variable 5_6 equal 5.0/6.0
variable 1_12 equal 1.0/12.0
variable 5_12 equal 5.0/12.0
```

```
lattice custom 1.0 &
a1 $a 0.0 0.0 &
a2 0.0 $b 0.0 &
a3 0.0 0.0 $c &
basis 0.0 0.0 0.0 &
basis 0.5 0.5 0.0 &
basis ${1_3} 0.0 0.5 &
basis ${5_6} 0.5 0.5 &
basis 0.0 0.0 0.625 &
basis 0.5 0.5 0.625 &
basis ${1_3} 0.0 0.125 &
basis ${5_6} 0.5 0.125
```

```
region myreg block 0 1 0 1 0 1
create_box 2 myreg
create_atoms 1 box &
basis 5 2 &
basis 6 2 &
basis 7 2 &
basis 8 2
```

```
```