Cs₂Pb(CO₃)₂: a novel mixed-metal carbonate with rare Pb-C-O one-dimensional chain

Carbonates deserve to be pursued in the exploration of candidate systems for birefringent crystalline materials. Recently, we successfully obtained a novel example of a mixed-metal carbonate, Cs₂Pb(CO₃)₂, using a high-temperature solution method in a closed system. Structural analysis shows that the rare Pb-C-O one-dimensional chain structure is formed by interconnecting the fundamental building blocks of PbC₂O₈. Detailed structural analyses and comparisons suggest a non-coplanar arrangement of CO₃ due to the highly distorted polyhedra formed by Pb²⁺. Theoretical calculations indicate that Cs₂Pb(CO₃)₂ exhibits an average calculated birefringence of 0.037 @ 1.64 nm, which is consistent with the conclusions deduced from the structure. The source of the properties is further elucidated through real-space atom cutting. This work provides a good reference idea for designing and synthesizing new carbonate optical crystal materials.