Crystal lattice parameters (a), Pb–Pb bond length (d₁), Pb–CX₃ bond length (d₂), buckling height (δ₁), energy bandgap with spin–orbit coupling (E_g), the formation energy (ΔE) and topological invariant for different PbCX₃ monolayers.

Monolayer	a (Å)	d 1 (Å)	d 2 (Å)	δ 1 (Å)	E g (SOC)	ΔE (eV per atom)
Pb	4.92845	3.02	—	1.0071	0.3229	—	0
PbCH3	5.07407	3.06	2.31	0.8863	0.9818	−1.3001	1
PbCF3	5.12554	3.06	2.37	0.7904	0.9692	−2.42002	1
PbCCl3	5.7454	3.34	2.40	0.406	0.841386	−1.70637	1