Electrical conductivity of MgCO3 under thermodynamic conditions of Earth’s interior: a first-principles investigation

The electrical conductivity of magnesite (MgCO3), magnesium carbonate, was investigated under the thermodynamic conditions of the Earth’s interior, within the framework of density functional theory (DFT) and Boltzmann transport theory. The results show that the conductivity of MgCO3 decreases under pressure and increases under the effect of temperature (depth of the lower mantle). Pressure plays a central role in controlling the conductivity of this mineral by modifying its electronic properties, such as the band structure and electronic density of states. Furthermore, the structural phase transition from the low-pressure magnesite-I (M-I) to the high-pressure magnesite-II (M-II) phase leads to a pronounced reduction in the electrical conductivity of MgCO3. The conductivity of the M-I phase is consistently greater than that of the M-II, and this trend persists by modifications in the respective electronic properties as a result of pressure changes. These findings suggest that magnesite (MgCO3) may have a minor contribution to the observed increase in electrical conductivity with depth in the lower mantle. Therefore, the electrical conductivity profile of the lower mantle is likely controlled by other minerals.