Abstract
We investigate the variable temperature (100–450 K) and high-pressure (
p
= ambient − 0.74 GPa) crystal chemistry of the black perovskite formamidinium lead iodide, [(NH
2
)
2
CH]PbI
3
, using single crystal X-ray diffraction. In both cases we find a phase transition to a tetragonal phase. Our experimental results are combined with first principles calculations, providing information about the electronic properties of [(NH
2
)
2
CH]PbI
3
as well as the most probable orientation of the [(NH
2
)
2
CH]
+
cations.