While a great body of research has been devoted to the study of
and search for design principles for polar and ferroelectric oxide
perovskites, polar or ferroelectric fluoride perovskites have not
received nearly as much attention. There are about 120
combinations of monatomic cations A+ and B2+ that, if
combined with F− in the stoichiometry ABF3, would exhibit
Goldschmidt tolerance factors1 between 0.76 and 1.13, the
criterion for stability for fluoride perovskites.2 Between the
Inorganic Crystal Structure Database3 and the Landolt−
Bö
rnstein tables,4 we located structural reports for nearly 70
stoichiometric ABF3 perovskites. The great majority of these
reports are for experimentally synthesized structures characterized
at room temperature. Computational and low-temperature
reports are scarce.