Al2O3 rectangular lattice

Dear All

I am trying to build a rectangular lattice by using basic information of Primitive or Conventional unit cell of Al2O3 with lattice, create_atoms & basis commands in Lammps, but unfortunately I couldn’t do it yet. So I have built the hexagonal lattice in Avogadro software, but I couldn’t build the rectangular lattice from hexagonal.

I prefer to build an Al2O3 rectangular lattice with Lammps commands by using the information of primitive or conventional unit cell.

1- Please let me know what the commands are in lammps for building the Al2O3 rectangular crystal by following unit cell information.

2- I had tried to convert the hexagonal lattice to rectangular by software such as Avogadro and Crystalmaker, and even I had used the Xtal tool that proposed by Atomeye or the method that proposed by LPMD for convert a lattice to rectangular lattice, but unfortunately I couldn’t do it. I want to know in generally, how I can build a rectangular lattice by a hexagonal unit cell in software like Avogadro or Crystalmaker.

3- I think the space group is to define the distribution of atoms in unit cell from basis atoms, and it is important information to build a unit cell. How the lammps can create crystal without this information? Because of we define just the two basis atoms in conventional unit cell, but there are 30 atoms in conventional Al2O3 unit cell. (Maybe need to define the all of 30 atoms for basis)

Conventional Unit Cell:

Corundum - Al2O3 (hexagonal representation)

space group: 167, R¯3c, hexagonal

a=b=4.7602 , c=12.9933 (°A) 90 90 120

2 non equivalent atoms

Aluminium 0. 0. 0.35216

Oxygen 0.30621 0. 0.25

Read the lattice doc page carefully, you can basically do
anything you want with the "custom" option. Also, you
can look at Section 6.12 of the manual for info
about triclinic transformations in LAMMPS. When you
start generating atom coords, there is no substitute
for dumping them to a dump file, looking at the coords,
and visualizing to see if you are getting what you expect.

Steve

Dear steve
thanks for your reply. I tried to create a unit cell by following commands.
I have used the basis information of a conventional unit cell.

lattice custom 1 a1 4.76 0.0 0.0 a2 -2.38 4.122 0.0 a3 0.0 0.0 12.993 &
basis 0.00000 0.00000 0.35216 &
basis 0.30621 0.00000 0.25000

region box prism 0 4.76 0 4.122 0 12.993 -2.38 0 0 units box
create_box 2 box

create_atoms 1 region box basis 1 1
create_atoms 2 region box basis 2 2

the first basis is to locate Al and the second is to locate O.
I tried to assign the type 1 to first basis and type 2 to second basis by using 2 create_atoms command.

1- I always have just 1 type in the box. how I can assign the different type to diffident basis?

Thanks

Use "create_atoms 1 box basis 1 1 basis 2 2"

Ray

Dear Ray
Thanks . that is ok.
I have another question.
In basic information of my conventional unit cell I have 30 atoms that created from 2 basis atom and the space group.
because of there is no something like space group in Lammps I have defined all of the 30 atoms
by create_atoms and basis commands. I want to know, is this method is correct or there is a method to create the unit cell by the 2 basis atom.
thanks

I don't know much about space groups, but if you
mean only define 2 basis atoms, then apply space
group operations, like rotations, reflections, etc to generate
the 30-atom unit cell ... then no, LAMMPS will not do that.

Just list the 30 atoms in the unit cell and LAMMPS will
replicate it. If that is complex, then I would write a script
to generate the 30-atom version of the lattice command
from more compact space group operations. If you make
the script general enough to generate all the space group variants,
then other LAMMPS users might find it useful as a pre-processor
tool, so we could release it with the LAMMPS distro.

Steve