Structure of A2BX4 Ruddlesden-Popper hybrid halide perovskites

Here B is Sn or Pb, X is Br or I, A is a molecule with cationic tail (e.g. -NH3) fitting A-site and large body disrupting 3D packing. It is a stack of weakly interacting (0.2 eV/mol) 2D layers, each layer is a square lattice of BX6 corner-sharing octahedra with A cations. The parent structure of a single layer (CIF) has the minimal cell which contains one B atom and maximum symmetry which is p4/mmm layer group. It is a cubic perovskite with one translation vector removed. In parent structure notations, B occupies (1a)=(0,0,0) site, X occupies (2c)=(1/2,0,0) and (2d)=(0,0,z) sites, and the cationic tail of A sits at (2e)=(1/2,1/2,z) site. Interlayer packing is governed mainly by steric effects with the most common displacement of (1/2,1/2,z) in p4/mmm notations (CIF). For crystal structure analysis and prediction, the methodology is limited to maximum supercell of 2×2×2 (wrt to parent structure).

Notations

See notations common for all CMSOS projects here
Filename notations
Dataname notations
Computational methodology
Considered cations (XYZ files)

Results for A2SnI4

CIF files
Data table part 1: Unit cell parameters and symmetry
Data table part 2: Geometry of the first BX6 octahedron
Data table part 3: Geometry of octahedra and coordination of halides (average and min/max)
Data table part 4: Geometry of the first cation and symmetry deviation of other cations
Entire table as CSV file
Table of total energies in meV/cation relative to the most stable single-layer polymorph
Electronic density of states for single layers with different A-cations (50 meV line broadening): Cs (p4/mmm), Cs-a, PEA, MPEA