Abstract
Solid-state systems whose properties at high pressure (exceeding 1 GPa) mimic those of are of large importance in the study of the interior of planets. By means of density functional theory (DFT) calculations we studied the high-pressure properties of a analog, . We reproduce the phase-transition sequence previously reported for this compound (), and predict that it should undergo a two-step dissociation: decomposition into an equimolar mixture of and at 25.4 GPa, followed by a breakdown into and NaF at 66.8 GPa. These processes are analogous to those predicted for compressed . Moreover, both and are isostructural with analogous phases from the Mg-Si-O system. We also find that both these compounds are thermodynamically stable at ambient conditions () or at a low pressure of 19 GPa (). Our study indicates that could serve as a good low-pressure analog of exhibiting the same sequence of phase transitions, and pressure induced decomposition, but at pressures an order of magnitude lower.
- Received 8 June 2021
- Revised 6 September 2021
- Accepted 18 October 2021
DOI:https://doi.org/10.1103/PhysRevMaterials.5.113602
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