Redetermination of brackebuschite, Pb2Mn(3+)(VO4)2(OH)

Area of Science:

• Mineralogy
• Crystallography
• Crystal Chemistry

Background:

• Brackebuschite, ideally Pb2Mn(3+)(VO4)2(OH), belongs to a mineral group with a general formula A2M(T1O4)(T2O4)(OH, H2O).
• Previous structural data for brackebuschite lacked detailed accuracy, particularly regarding hydrogen bonding and atomic displacement parameters.

Purpose of the Study:

• To redetermine the crystal structure of brackebuschite using single-crystal X-ray diffraction.
• To refine anisotropic displacement parameters and locate the hydrogen atom for improved accuracy.
• To elucidate the hydrogen-bonding scheme and understand the structural role of the hydroxyl group.

Main Methods:

• Single-crystal X-ray diffraction on a natural brackebuschite sample.
• Refinement of anisotropic displacement parameters for non-hydrogen atoms.
• Location and refinement of the hydrogen atom position.

Main Results:

• The crystal structure was refined to a higher accuracy, improving upon previous results.
• An unambiguous hydrogen-bonding scheme was established.
• The structure features infinite chains of edge-sharing [Mn(3+)O6] octahedra decorated by VO4 tetrahedra, linked by Pb polyhedra.

Conclusions:

• The refined crystal structure of brackebuschite provides a detailed understanding of its atomic arrangement and bonding.
• The study confirms the mineral's unique structural features, including Mn-V-O chains and Pb-O polyhedra.
• The findings agree with Raman spectroscopic data, validating the structural model and hydrogen bonding interactions.