Pressure-induced hydrogen bond symmetrisation in guyanaite, β-CrOOH: evidence from spectroscopy and ab initio simulations
Jahn, Sandro; Wunder, Bernd; Koch-Müller, Monika; Tarrieu, Leïla; Pöhle, Michael; Watenphul, Anke; Taran, Michael N.
European Journal of Mineralogy Volume 24 Number 5 (2012), p. 839 - 850
published: Oct 1, 2012
ArtNo. ESP147052405009, Price: 29.00 €
Guyanaite, β-CrOOH, is a structural analogue of the high-pressure oxyhydroxide phases δ-AlOOH and ε-FeOOH. Here, it was synthesized in piston-cylinder and multi-anvil press experiments at 4-13.5 GPa and 900-1100 C. The deuterated phase β-CrOOD was synthesized at 4 GPa and 600 C. The samples were characterized at ambient conditions by X-ray diffraction, diffuse optical reflectance spectroscopy and infrared absorption (IR) spectroscopy. In addition, the structural evolution of β-CrOOH and β-CrOOD with increasing pressure up to about 20 GPa was studied by in situ IR spectroscopy in a diamond anvil cell (DAC). This investigation was complemented by first-principles calculations in the framework of the density-functional theory (DFT). A pronounced geometric isotope effect and very short O-H. . . O bond lengths of 2.497(3) Å for β-CrOOH and 2.541(3) Å for β-CrOOD are observed at ambient pressure. In the IR spectra, no bands show up above 2000 cm