Amorphous carbonates phases are of significant interest in the technological sector due their appearance in a number of processes, such carbon storage and biomineralization. However, the disordered atomic structural nature of these phases makes it difficult to accurately determine the exact local bonding environments that are present. Atomistic simulation techniques are capable of providing models for the local atomic structure, yet, without any active feedback mechanisms from experimental data, these models tend to remain qualitatively accurate due to the metastable nature of the materials. Furthermore, amorphous structural models derived direct from X-ray/neutron scattering data lack information regarding their thermodynamic plausibility. Here, the structure of a hydrated amorphous magnesium carbonate phase (MgCO3·3D2O) is determined by actively combining computational chemistry (density functional theory) and pair distribution function analysis in an iterative manner in order to explore the potential energy landscape of this material. By utilizing the iterative methodology we reveal that the structure is heterogeneous at the atomic level, consisting of ‘nanopores’ of water molecules interspersed in a Mg2+/CO32-rich framework structure. This heterogeneity at the atomic length scale is likely to contribute to the dehydration of hydrated magnesium carbonate by providing a route for water molecules to be removed.

Uncovering the local atomic structure of a hydrated amorphous magnesium carbonate: The computational chemistry and total scattering iterative methodology

249th National Meeting (2015)

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