Finding Structural Phase Transitions in Barlowite and Claringbullite*

Barlowite (Cu₄(OH)₆FBr) and claringbullite (Cu₄(OH)₆FCl) are minerals related to the quantum spin liquid candidate herbertsmithite ZnCu₃(OH)₆Cl₂, the popular S = ½ antiferromagnet with a geometrically perfect kagome lattice. The kagome lattices of claringbullite and barlowite are stacked perfectly on top of one another, separated by planes consisting of Cu²⁺ and halide ions, and show promise as QSL candidates. Both materials have a hexagonal crystal structure with P6₃/mmc symmetry and undergo temperature-dependent phase transitions to Pnma symmetry1. Previously we examined the barlowite transitions at 276 K¹, but the claringbullite transition occurs much lower. To pinpoint the transition, equipment had to be modeled and aligned.

Chem. Commun., 2019,55,11587-11590