期刊
PHYSICAL REVIEW B
卷 98, 期 5, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.98.054102
关键词
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资金
- U.S. Department of Energy [DE-NA0001982]
- Novartis Universitat Basel Excellence Scholarship for Life Sciences
- Swiss National Science Foundation [P300P2-158407P300P2-174475, P300P2-174475]
- National Science Foundation [OCI-1053575]
- NSF [ACI-1445606]
- National Energy Research Scientific Computing Center [DE-AC02-05CH11231]
Recently reported synthesis of FeO2 at high pressure has stimulated great interest in exploring this new iron oxide and elucidating its properties. Here, we present a systematic computational study of crystal structure, chemical bonding, and sound velocity of FeO2 in a wide range of pressure. Our results establish thermodynamic stability of the experimentally observed pyrite phase (P-phase) of FeO2 at pressures above 74 GPa and unveil two metastable FeO2 phases in Pbcn and P4(2)/mnm symmetry at lower pressures. Simulated x-ray diffraction (XRD) spectra of Pbcn and P4(2)/mnm FeO2 match well with measured XRD data of the decompression products of P-phase FeO2, providing compelling evidence for the presence of these metastable phases. Energetic calculations reveal unusually soft O-O bonds in P-phase FeO2 stemming from a low-frequency libration mode of FeO6 octahedra, rendering the O-O bond length highly sensitive to computational and physical environments. Calculated sound-velocity profiles of P-phase FeO2 are markedly different from those of the Pbcn and P4(2)/mnm phases, underscoring their distinct seismic signatures. Our findings offer insights for understanding the rich structural, bonding, and elastic behaviors of this newly discovered iron oxide.
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