Metallization of Silica Analogue: High pressure study of Barium Iodide
Abstract
In this study we observed the transition from an insulating to metallic bonding type of BaI2. To document the metallization of this compound, we use an absorption edge infrared spectroscopy technique to observe the closure of bandgap with increasing pressure. BaI2 is expected to become fully metallic under 100 GPa, which would be the lowest metallization pressure of the AX2compound group. Band gap measured as a function of pressure will be compared with results from first principles quantum mechanical calculations. The Chemical bonding properties of materials of large Exo-planets are difficult to study directly; the bulk of the rocky material is believed to be siliceous, but the physical properties of silica are not well understood at high pressures and temperatures.Rrecent studies suggest that silica transforms from an insulating to a metallic state at high pressures. With the distinction between a planetary core and its mantle characterized by the type of chemical bonding as well as composition, this change in chemical bonding type is profound in planetary sciences. Although the high-pressure structures of SiO2 are not well known past the stishovite phase, the AX2 analogs like BaI2 have been observed to follow a systematic sequence of high-pressure transformations with a succession of coordination changes. The sequence is well- established up to the cotunnite phase (orthorhombic structure, space group: Pnma), the highest-coordination structure observed in AX2 compounds at ambient pressure (predicted to be acquired in SiO2 by 750 GPa). This makes materials that possess the cotunnite structure, as BaI2 does at ambient conditions useful as structural analogs to silica.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMMR21B2653S
- Keywords:
-
- 3909 Elasticity and anelasticity;
- MINERAL PHYSICSDE: 3924 High-pressure behavior;
- MINERAL PHYSICSDE: 3939 Physical thermodynamics;
- MINERAL PHYSICSDE: 3630 Experimental mineralogy and petrology;
- MINERALOGY AND PETROLOGY