Quantum chemical study of thermal decomposition mechanism and polymorph predict phase transitions of magnesite

Mass-independent fractionation of oxygen isotopes during thermal decomposition of divalent metal carbonates: Crystallographic influence, potential mechanism and cosmochemical significance

“…Strong support for such a mechanism is provided by its compatibility with recent studies of the thermal decomposition of calcite (Zhao et al, 2013;Wang et al, 2017;Li et al, 2018) and magnesite (Zhao et al, 2015). In these investigations, the decomposition mechanism was found to proceed via the reaction sequence (using MgCO3 as the example; Zhao et al, 2015): Substitution of numerical values, with 𝑔 for a free electron, gives, for a magnetic flux density of 1 mT, a frequency of: (10 -9 × 2.00232 × 9.27401 × 10 -24 ) / (6.62607 × 10 -34 ) = 28.025 MHz .…”

“…Conversely, quantum chemical modelling of the thermal decomposition of magnesite have shown that a structural phase transition from the rhombohedral form to a chiral orthorhombic structure occurs during the thermal decomposition process (Zhao et al, 2015).…”

“…Whereas there have been numerous investigations of the thermal decomposition of divalent metal carbonates (especially of calcite) over many decades, details of the mechanism remain largely conjectural. Recent quantum chemical modelling of the thermal decomposition of calcite (Zhao et al, 2013) and magnesite (Zhao et al, 2015), involving detailed potential energy surface calculations, have explored the relative feasibility of different reaction pathways. These theoretical studies provide valuable information towards elucidating the decomposition mechanism at the molecular level.…”