The crushing pressures and intense temperatures in Earth’s deep interior squeeze atoms and electrons so closely together that they interact very differently. With depth materials change. New experiments and supercomputer computations discovered that iron oxide undergoes a new kind of transition under deep Earth conditions. Iron oxide, FeO, is a component of the second most abundant mineral at Earth’s lower mantle, ferropericlase. The finding, published in an upcoming issue of Physical Review Letters, could alter our understanding of deep Earth dynamics and the behavior of the protective magnetic field, which shields our planet from harmful cosmic rays.
Ferropericlase contains both magnesium and iron oxide. To imitate the extreme conditions in the lab, the team studied the electrical conductivity of iron oxide to pressures and temperatures up to 1.4 million times atmospheric pressure and 4000°F—on par with conditions at the core-mantle boundary. They also used a new computational method that uses only fundamental physics to model the complex many-body interactions among electrons. The theory and experiments both predict a new kind of metallization in FeO.
But, as the team outlined in Physical Review Letters, the metal's structure was surprisingly unchanged. The finding could have implications for our as-yet incomplete understanding of how the Earth's interior gives rise to the planet's magnetic field.
While many transitions are known in materials as they undergo nature's extraordinary pressures and temperatures, such changes in fundamental properties are most often accompanied by a change in structure. These can be the ways that atoms are arranged in a crystal pattern, or even in the arrangement of subatomic particles that surround atomic nuclei.
Ferropericlase contains both magnesium and iron oxide. To imitate the extreme conditions in the lab, the team studied the electrical conductivity of iron oxide to pressures and temperatures up to 1.4 million times atmospheric pressure and 4000°F—on par with conditions at the core-mantle boundary. They also used a new computational method that uses only fundamental physics to model the complex many-body interactions among electrons. The theory and experiments both predict a new kind of metallization in FeO.
But, as the team outlined in Physical Review Letters, the metal's structure was surprisingly unchanged. The finding could have implications for our as-yet incomplete understanding of how the Earth's interior gives rise to the planet's magnetic field.
While many transitions are known in materials as they undergo nature's extraordinary pressures and temperatures, such changes in fundamental properties are most often accompanied by a change in structure. These can be the ways that atoms are arranged in a crystal pattern, or even in the arrangement of subatomic particles that surround atomic nuclei.
Compounds typically undergo structural, chemical, electronic, and other changes under these extremes. Contrary to previous thought, the iron oxide went from an insulating (non-electrical conducting) state to become a highly conducting metal at 690,000 atmospheres and 3000°F, but without a change to its structure. Previous studies had assumed that metallization in FeO was associated with a change in its crystal structure. This result means that iron oxide can be both an insulator and a metal depending on temperature and pressure conditions.
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