The influence of pressure on the structure and dynamics of hydrogen bonds in zoisite and clinozoisite |
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| Authors: | Björn Winkler Julian D Gale Keith Refson Dan J Wilson Victor Milman |
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| Institution: | 1.Institut für Geowissenschaften,Universit?t Frankfurt,Frankfurt a.M.,Germany;2.Nanochemistry Research Institute,Curtin University of Technology,Perth,Western Australia;3.STFC Rutherford Appleton Laboratory,Oxon,England;4.Accelrys Inc.,Cambridge,UK |
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| Abstract: | Density functional theory calculations have been used to study the pressure-induced changes of the hydrogen bond of Fe-free
orthozoisite and clinozoisite and the concomitant shifts of the OH-stretching frequencies. Two independent parameter-free
lattice dynamical calculations have been employed. One was based on a plane-wave basis set in conjunction with norm-conserving
pseudopotentials and a density functional perturbation theory approach, while the other used a localised basis set and a finite
displacement algorithm for the lattice dynamical calculations. Both models confirm the unusually large pressure-induced red-shift
found experimentally (−33.89 cm−1/GPa) in orthozoisite, while the pressure-induced shifts in clinozoisite are much smaller (−5 to −9 cm−1/GPa). The atomistic model calculations show that in orthozoisite the nearly linear O–H⋯O arrangement is compressed by about
8% on a pressure increase to 10 GPa, while concomitantly the O–H distance is significantly elongated (by 2.5% at 10 GPa).
In clinozoisite, the O–H⋯O arrangement is kinked  at ambient conditions and remains kinked at high pressures, while the O-H distance is elongated by only 0.5% at 10 GPa. The
current calculations confirm that correlations between the distances and dynamics of hydrogen bonds, which have been established
at ambient conditions, cannot be used to infer hydrogen positions at high pressures. |
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| Keywords: | Zoisite High pressure Hydrogen bond Lattice dynamics |
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