• journal_title：Mineralogical Magazine
• Contributor：W. A. Crichton ; J. B. Parise ; H. Müller ; J. Breger ; W. G. Marshall ; M. D. Welch
• Publisher：Mineralogical Society of Great Britain and Ireland
• Date：2012-
• Format：text/html
• Language：en
• Identifier：10.1180/minmag.2012.076.1.25
• journal_abbrev：Mineralogical Magazine
• issn：0026-461X
• volume：76
• issue：1
• firstpage：25
• section：Articles

Magnesium hydroxyfluoride, Mg(OH)F, has been synthesized by a subcritical hydrothermal route from a 1:1 molar mixture of brucite, Mg(OH)₂, and sellaite, MgF₂ with a rutile type structure, in excess water. Using a combination of synchrotron X-ray and time-of-flight neutron powder diffraction, the structure of Mg(OH)F has been solved in the diaspore space group m>Pnmam> with m>am> = 10.116(3), m>bm> = 4.6888(10) and m>cm> = 3.0794(7) Å at ambient conditions. The most intense diffraction lines are [m>dm>_obs (m>hklm>) m>Im>_obs]: 2.291 (211) 10, 4.253 (101) 7, 1.747 (212) 7, 2.229 (401) 6 and 1.480 (610) (4) Å, with the largest m>dm>-spacing at 5.058 Å. Sharp infrared stretching bands are located at 3679 and 3645 cm ⁻¹, with a broader band at 3535 cm ⁻¹. The topology of the structure is intermediate between that of the OH and F endmembers, being derived through notional shearing nearly normal to the sheets of octahedra of the CdI₂/Mg(OH)₂-type structure. Further similar shearing at an interval ½m>am> would lead to a Cd(OH)F-type structure, which is also related to the rutile structure type. The observations and model presented here indicate a close correlation between the structural properties of the endmembers and Mg(OH)F.