PBE-GGA Predicts the B8$\leftrightarrow$B2 Phase Boundary of FeO at Earth's Core Conditions
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arXiv
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| Autori principali: | , , |
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| Natura: | Preprint |
| Pubblicazione: |
2022
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| _version_ | 1866909214189813760 |
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| author | Zhang, Zhen Sun, Yang Wentzcovitch, Renata M. |
| author_facet | Zhang, Zhen Sun, Yang Wentzcovitch, Renata M. |
| contents | FeO is a crucial phase of the Earth's core, and its thermodynamic properties are essential to developing more accurate core models. It is also a notorious correlated insulator in the NaCl-type (B1) phase at ambient conditions. It undergoes two polymorphic transitions at 300 K before it becomes metallic in the NiAs-type (B8) structure at $\sim$100 GPa. Although its phase diagram is not fully mapped, it is well established that the B8 phase transforms to the CsCl-type (B2) phase at core pressures and temperatures. Here we report a successful \textit{ab initio} calculation of the B8$\leftrightarrow$B2 phase boundary in FeO at Earth's core pressures. We show that fully anharmonic free energies computed with the PBE-GGA + Mermin functional reproduce the experimental phase boundary within uncertainties at $P > 240$ GPa, including the largely negative Clapeyron slope of $-52 \pm 5$ MPa/K. This study validates the applicability of a standard DFT functional to FeO under Earth's core conditions and demonstrates the theoretical framework that enables complex predictive studies of this region. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2211_15052 |
| institution | arXiv |
| publishDate | 2022 |
| record_format | arxiv |
| spellingShingle | PBE-GGA Predicts the B8$\leftrightarrow$B2 Phase Boundary of FeO at Earth's Core Conditions Zhang, Zhen Sun, Yang Wentzcovitch, Renata M. Materials Science Geophysics FeO is a crucial phase of the Earth's core, and its thermodynamic properties are essential to developing more accurate core models. It is also a notorious correlated insulator in the NaCl-type (B1) phase at ambient conditions. It undergoes two polymorphic transitions at 300 K before it becomes metallic in the NiAs-type (B8) structure at $\sim$100 GPa. Although its phase diagram is not fully mapped, it is well established that the B8 phase transforms to the CsCl-type (B2) phase at core pressures and temperatures. Here we report a successful \textit{ab initio} calculation of the B8$\leftrightarrow$B2 phase boundary in FeO at Earth's core pressures. We show that fully anharmonic free energies computed with the PBE-GGA + Mermin functional reproduce the experimental phase boundary within uncertainties at $P > 240$ GPa, including the largely negative Clapeyron slope of $-52 \pm 5$ MPa/K. This study validates the applicability of a standard DFT functional to FeO under Earth's core conditions and demonstrates the theoretical framework that enables complex predictive studies of this region. |
| title | PBE-GGA Predicts the B8$\leftrightarrow$B2 Phase Boundary of FeO at Earth's Core Conditions |
| topic | Materials Science Geophysics |
| url | https://arxiv.org/abs/2211.15052 |