Nelson, JR;
Needs, RJ;
Pickard, CJ;
(2015)
Calcium peroxide from ambient to high pressures.
Physical Chemistry Chemical Physics
, 17
(10)
pp. 6889-6895.
10.1039/c4cp05644b.
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Abstract
Structures of calcium peroxide (CaO2) are investigated in the pressure range 0-200 GPa using the ab initio random structure searching (AIRSS) method and density functional theory (DFT) calculations. At 0 GPa, there are several CaO2 structures very close in enthalpy, with the ground-state structure dependent on the choice of exchange-correlation functional. Further stable structures for CaO2 with C2/c, I4/mcm and P21/c symmetries emerge at pressures below 40 GPa. These phases are thermodynamically stable against decomposition into CaO and O2. The stability of CaO2 with respect to decomposition increases with pressure, with peak stability occurring at the CaO B1-B2 phase transition at 65 GPa. Phonon calculations using the quasiharmonic approximation show that CaO2 is a stable oxide of calcium at mantle temperatures and pressures, highlighting a possible role for CaO2 in planetary geochemistry. We sketch the phase diagram for CaO2, and find at least five new stable phases in the pressure-temperature ranges 0 ≤ P ≤ 60 GPa, 0 ≤ T ≤ 600 K, including two new candidates for the zero-pressure ground state structure.
| Type: | Article |
|---|---|
| Title: | Calcium peroxide from ambient to high pressures |
| Location: | England |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1039/c4cp05644b |
| Publisher version: | http://dx.doi.org/10.1039/c4cp05644b |
| Language: | English |
| Additional information: | This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences |
| URI: | https://discovery.ucl.ac.uk/id/eprint/1468861 |
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