# Query regarding placing an impurity

Hi Steve,

I have a simple query regarding placing an impurity on a simple lattice. For example,

To specify the bcc lattice i used the following command.

lattice custom 1 a1 1 0 0 a2 0 1 0 a3 0 0 1 origin 0 0 0 basis 0 0 0 basis 0.5 0.5 0.5.

Now i wish to create only single impurity on single face of cube so i specified.

lattice custom 1 a1 1 0 0 a2 0 1 0 a3 0 0 1 origin 0 0 0 basis 0 0 0 basis 0.5 0.5 0.5 basis 0.5 0.5 0
which created two impurities on both faces. How can one of them be deleted & bulk be generated.

Regards,
Saurav

I can't tell if you are trying to define two different lattices
and create 2 different sets of atoms. The usual way
to do this is to define one lattice with all the atoms of
both types in the basis.

Then with the create_atoms command you can create
two types of atoms at once, using its "basis" keyword
to specify different atom types for different basis sites
in the lattice definition.

Steve

Hi Steve,

I think you got me wrong. Let me simplify.

lattice custom 1 a1 1 0 0 a2 0 1 0 a3 0 0 1 origin 0 0 0 basis 0 0 0 basis 0.5 0.5 0.5 basis 0.5 0.5 0
It will create a bcc lattice + 2 atoms on faces as shown in attached snap(before.jpg)

However, I wish to have only one atom on the face as shown in attached snaps(after.jpg) & to generate a bulk. How should i do it.

Regards,
Saurav

If i specify

Hi Steve,

I think you got me wrong. Let me simplify.

lattice custom 1 a1 1 0 0 a2 0 1 0 a3 0 0 1 origin 0 0 0 basis 0 0 0 basis 0.5 0.5 0.5 basis 0.5 0.5 0

It will create a bcc lattice + 2 atoms on faces as shown in attached snap(before.jpg)

However, I wish to have only one atom on the face as shown in attached snaps(after.jpg) & to generate a bulk. How should i do it.

Regards,
Saurav

If i specify

If your unit cell is the cube in the picture, then it's not possible
to define a basis atom on a face that won't be on multiple faces
in the replicated lattice. That's not what a unit cell and basis
atoms mean. You'd have to define a 2nd lattice with a larger unit
cell and put the impurity atom in the middle of the larger cell
to get what you want. Which you can easily do with LAMMPS.

Steve