Volume 102, Number 3, May 2013
|Number of page(s)||4|
|Section||Condensed Matter: Structural, Mechanical and Thermal Properties|
|Published online||16 May 2013|
The new phase of HgF2 at high pressure
1 Institute of Condensed Matter Physics, Linyi University - Linyi 276005, PRC
2 Beijing Computational Science Research Center - Beijing, 100084, PRC
3 State Key Lab of Superhard Materials, College of Physics, Jilin University - Changchun 130012, PRC
4 Department of Physics and Materials Science, City University of Hong Kong - Hong Kong SAR, China
Received: 25 March 2013
Accepted: 23 April 2013
Mercury halides form an amazing number of solid phases and remarkably only the crystal structure of HgF2 at high pressure is not established. We here report a stabilization HgF2 high-pressure phase predicted by the density functional structural searches, which adopts the Pnma symmetric structure (12 atoms/cell, α-PbCl2–type, or cotunnite). The phase transition from the ambient conditions phase Fm-3m (phase I) to the Pnma phase (phase II) was confirmed at 4.7 GPa. The calculated equation of state suggests that this is a first-order phase transition. At this phase transition, the coordination number of Hg2+ increases from eight to nine, similar to the phase transition sequence of CaF2. Furthermore, a thorough CALYPSO structural search up to 100 GPa cannot find any other structure that is more stable than the Pnma structure.
PACS: 61.50.Ks – Crystallographic aspects of phase transformations; pressure effects / 71.15.Mb – Density functional theory, local density approximation, gradient and other corrections / 71.20.-b – Electron density of states and band structure of crystalline solids
© EPLA, 2013
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