Estimation of A cation radii in APbX₃.

r Pb a	Xa	r A b for t = 0.8	r A b for t = 1.0
Pb2+ (1.19 Å)	Cl− (rCl = 1.81 Å)	1.58 Å	2.43 Å
	Br− (rBr = 1.96 Å)	1.60 Å	2.50 Å
	I− (rI = 2.20 Å)	1.64 Å	2.59 Å

^aEffective ionic radii for coordination number of 6.

^{b 50,51}