Abstract
The structure, electrical properties, elasticity, and anisotropy of the newly discovered mantle mineral, CaO3, are obtained under 10–50 GPa by first-principles simulation to understand their relations with the composition and structure of the mantle transition zone. Crystal structure and phonon frequencies under 0–50 GPa indicate that CaO3 can exist stably under 10–50 GPa. Here, the band gap of CaO3 is 2.32–2.77 under the explored pressure and indicates its semiconductor property. The Mulliken population analysis shows that the Ca–O bond is an ionic bond, and O–O bond is a covalent bond, and the strength of the O–O bond is higher than that of the Ca–O bond. The density, bulk modulus, and shear modulus of CaO3 increase with increasing pressure. The compressional wave velocity (Vp) and shear wave velocity (Vs) of CaO3 increase with increasing pressure. The seismic wave velocity of CaO3 is smaller than that of the Preliminary Reference Earth Model (PREM) and common mantle transition zone minerals, and it is a very exceptional low seismic wave velocity phase. The anisotropies of Vs are 36.47, 26.41, 23.79, and 18.96%, and the anisotropies of Vp are 18.37, 13.91, 12.75, and 10.64% under 15, 25, 35, and 50 GPa, respectively. Those seismic velocity anisotropies are larger than those of the mantle transition zone’s main component, so CaO3 may be an important source of seismic wave velocity anisotropy in the mantle transition zone. Our results provide new evidence for understanding the material composition and the source of anisotropy in the mantle transition zone.
Highlights
The research studies on the physical and chemical behavior of rocks and minerals under deep Earth conditions through high-temperature and high-pressure experiments and simulation are two of the important ways to understand the composition, structure, and dynamic processes of the Earth
The Mulliken population analysis shows that the Ca–O bond is an ionic bond, and the O–O bond is a covalent bond (Table 2), and the strength of the O–O bond is higher than that of the Ca–O bond
The existence of the CaO3 in the mantle may lead to the formation of a low velocity zone because of its low seismic wave velocity
Summary
The research studies on the physical and chemical behavior of rocks and minerals under deep Earth conditions through high-temperature and high-pressure experiments and simulation are two of the important ways to understand the composition, structure, and dynamic processes of the Earth. Due to the difficulty in entering the Earth’s interior, most of our understanding of the Earth’s interior derives from seismic and geophysical observation. By comparing observed seismic properties of the Earth with properties of particular minerals under deep Earth conditions, the physical and chemical properties of the Earth can be constrained (Sun, 2019). The mantle transition zone is a particular area in the Structure and Elasticity of CaO3 mantle with a particular structure and composition (Birch, 1952; Frost, 2008). The mantle transition zone refers to the part of the
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