Partial occupancy & simulation box

LAMMPS LAMMPS Beginners
1

Hello I am a beginner in LAMMPS and have been trying to create a 2x2x2 simulation box (thus containing 2 unit cells of the compound). In the past I used basis option in lattice command to specify the coordinates and region command to define the size. But now I need to define partial occupancies for some of the elements in the compound. I couldn’t figure out how to specify partial occupancy unless I use the “read_data” command to read the CIF file I had generated. Now how do I create a 2x2x2 simulation cell in this?

Is there a way to use “read_data” command combined with Lattice & region command so that the former takes care of partial occupancy and the later takes care of number of unit cell/simulation box size? Is there some other way to do this?

Thanks in advance

2

That would be 8 times the unit cell, not 2.

Each lattice position with partial occupancy should be given its own atom type. Then you can use the set command to change those at a given ratio. And then delete atoms with such type, if needed.

For more complex situations, you are better off creating a data file with an external tool like Atomsk.

3

Thanks a lot !