Computational Lab 3

Periodic Boundary Conditions-Local Optimization of Bulk Gold and Gold surfaces with DFT

Part 5: Effect of binding sites

1. Create a new directory called Slab111_O_hollow. Copy the INCAR, KPOINTS, CONTCAR and frilab2.sub from Slab111 into Slab111_O_hollow. Next, change the name of the CONTCAR file to POSCAR.
2. Next, edit your POSCAR and POTCAR files so that oxygen binds to the surface at a hollow site. You can add the oxygen atom the same way you added the OH group.

   The hollow site on FCC 111 surface is between 3 atoms. In ase gui, you can add the oxygen atom directly at the hollow site by selecting the 3 atoms that surrounds the hollow site and then add the atom. When you do this, the newly added atom is at the center of the selected atoms. You need to move this atom up some what, so that its distance to the surface atoms is at least 1 Å.

3. Before submitting this VASP job, make two copies of the Slab111_O_hollow directory called Slab111_O_bridge and Slab111_O_top.
   
   
4. Edit the files in Slab111_O_bridge and Slab111_O_top such that the oxygen is close to a bridge and top site respectively.

   Bridge sites are between two atoms and top site is directly on top of an atom.

5. Once the appropriate files are set up, optimize each structure at the various binding sites on the Au surface.

   To calculate the binding energies of different surfaces, you can use an Excel spread sheet to manage your data.