Wrong space group ? P3m1 / P63mmc

[rogeriog]

I am interested in 2D materials such as Cs3Sb2I9 (P-3m1). I found some materials that would fit into this structure from the provided data, such as Cs3InIrBr9 (P-3m1) and Rb3ScIrBr9 (P-3m1). However, when I look at the CIF file, it instead appears to be very similar to Cs3Sb2I9 (P63mmc), which is a 0D material. This pattern repeats for all A3B2X9 (P-3m1) materials I've checked so far in the dataset. I show this figure to better illustrate.

Am I misunderstanding something?

PS: the P63mmc form is more stable in the case of Cs3Sb2I9, so it would be expected for the 0D form to be in the convex hull instead of P-3m1, although of course this is not rule.

[blokhin]

Space group selection uncertainty for this structure type is known in the literature (see e.g. [1] vs [2]). In fact, this is because P-3m1 is a subgroup of P63/mmc. In turn, this should be manifested from the first principles in a slightly deeper minimum at zero Kelvin for the former structure being relaxed as compared to the latter structure.