1    2     3     4    

6. Press CP to perform calculation of the 1st and 2nd lattice vectors to be within the plane. Then press Q to leave the menu.

When returning to the main menu, the CURRENT lattice vectors will change into the new ones. The system will also be rotated such that these two vectors are in the XY plane.  The surface lattice vectors are generated!

7. Enter Co to check the atomic  positions and lattice vectors

8. We can now preview the structure with XMakemol

It is possible that the atoms are located in different equivalent positions. Tetr has the option Re from the main menu to redefine the atoms in the equivalent positions so that the atoms are shifted by lattice vectors to stay in the same unit cell.

CO3

CO3

C

C

9. Still the surface is not ready. First, we need to create the (3x2) supercell with the 3 bulk layers with the Ex option.  When prompted, type  three pairs of numbers:  0   2 , then 0    1,  followed by -2    0. The first two pairs expand the surface along the first two lattice vectors three- and two-fold, respectively. The last pair expands the cell along the third lattice (out of plane) three-fold to have three cells in the slab. Then preview the structure! (recall that the xyz file is updated  automatically every time a change is made!)

Note 1: as a first try, before using the Ex command, use  Bb  first. Preview the structure and make sure that you created the desired supercell. Remember, that if you used the Ex command and realized that the structure is wrong, you can always press the U command to undo the action. 

10. With option 8 you create the slab by separating out the layers and creating the vacuum gap. Tetr  asks you which vector you want to change.

11. Type 3 and choose the size of the gap (in our case 30) . Tetr will also ask you to confirm your change.