I am currently trying to create a CeO2 (100) / CoO (200) interface for a bulk oxide. Unlike what I usually see, slabs stacked on the z-axis ("vertically"), I would like to stack the two "horizontally", in this case along the x-axis, so that both desired split surfaces are exposed to possible adsorption. I show here an image (z-view) of the system generated via the ASE. The slab was generated from .cif files of CoO and CeO2, cleaved to the desired indices and merged.
Although I have been working with VASP for a few years now, this is the first time I have approached systems of this type. In fact, I soon realised that it is not at all easy, as CoO has a smaller lattice constant than CeO2, so you can clearly see that the structure undergoes strain. I thought of tackling the problem by
- create a zero vacuum cell (emulating bulk) with the slabs to optimise the positions and thus the cell parameters (perhaps a few cycles of calculations)
- at the end, add the vacuum in the z-direction to obtain the real slabs.
- Increase precision of the calculations (spin polarization, Hubbard, etc...)
My main concern is the validity of step 1. and how could i overcome it in case it is wrong. Because i am not sure surfaces are meant to be "bulk-like" stacked from the VASP PBC point of view.
At this point, is this the right way to proceed or is it a total dead end? Could anyone suggest a different workflow based on their previous experience, perhaps one that overcomes the problems of ion optimisation (always critical...) ? Unfortunately I have found relatively little information about this in the literature.
Thanks in advance.