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I'm trying to use pymatgen model to cleave a specific termination on Fe2O3 and Al2O3. In SlabGenerator, one of its parameter is in_unit_planes(bool), default =false.

It said in the instruction that I can set either in Angstrong or in a unit of hkl planes. Does anyone know what "in unit of hkl planes" means and how can I set up so that I can cleave a specific termination Al/Fe and Oxigen termination?

When I set the min_slab_size and min_vacuum_size, it returned a structure with too many layers and I couldn't determine the number of layers in the slab structure.

Chameera Dulanga
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Ngan Huynh
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In units of hkl means integer multiples of the hkl distance (e.g. in cubic system that is dhkl = a / (h2+k2+l2)1/2 where a is the lattice constant).

In fact, there is a function in PyMatGen that creates all possible surface terminations for you: get_slabs as part of the SlabGenerator class. More info can be found here.

There is actually an active community here to answer your questions regarding PyMatGen and the MaterialsProject.

Peter Schindler
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  • Thank you for your help! I tried those methods but it didnt generate the thinner slab as I want. For example, I use Al2O3 corundum convectional structure which has 18 layers. I just want to generate slabs with half or less layers to perform number of layers optimization. The SlabGenerator always returned 18 layers slab no matter how I changed the parameters. I asked everywhere I could and hope I would be able to find answer from the forum – Ngan Huynh Mar 24 '20 at 20:06
  • Oh, I see - I didn't know that your unit cell is that huge! Yes, I think that function would always return a slab with a thickness of at least 1 unit cell. I guess you can use the function to create an 18 layer thick slab of the preferred orientation and then you just delete atoms until you reach the desired thickness. However, if you have 18 layers that means there are 18 unique terminations? Also not sure what you mean by "number of layer optimization"? Optimization of which property? – Peter Schindler Mar 25 '20 at 02:05