The following figure is the bulk structure of NiSe$_2$ downloaded from the materials project database.
Now I want to study the properties of its  plane. In detial, I cut the slab with atomic simulation environment (ASE) as follows:
The cutted slab is:
In particular, I find the Se5 atom is strange. In additon, the cutted slab is different from this paper:
Here different terminations are considered. Therefore, how can I use ASE cut these (111) slabs with different terminations?
Thanks in advance.