Fluorine chemistry at extreme conditions: Possible synthesis of HgF4

Abstract

By irradiating a pressurized mixture of a fluorine-bearing compound (XeF2) and HgF2 with synchrotron hard x-rays (>7 keV) inside a diamond anvil cell, we have observed dramatic changes in the far-infrared spectrum within the 30-35 GPa pressure range which suggest that we may have formed HgF4 in the following way: XeF2hv−→Xe+F2 (photochemically) and HgF2+F2→HgF4 (30 GPa < P < 35 GPa). This lends credence to recent theoretical calculations by Botana et al. that suggest that Hg may behave as a transition metal at high pressure in an environment with an excess of molecular fluorine. The spectral changes were observed to be reversible during pressure cycling above and below the above mentioned pressure range until a certain point when we suspect that molecular fluorine diffused out of the sample at lower pressure. Upon pressure release, HgF2 and trace XeF2 were observed to be remaining in the sample chamber suggesting that much of the Xe and F2 diffused and leaked out from the sample chamber.

Keywords

• fluorine chemistry at extreme conditions
• mercury transition metal behavior
• diamond anvil cell
• high pressure
• infrared spectroscopy