A total scattering study of prenucleation structures in saturated aqueous magnesium sulfate - observation of extended clusters.

Autor: Irving DJM; School of Chemistry, University of Southampton, Southampton, SO17 1BJ, UK. M.E.Light@soton.ac.uk., Light ME; School of Chemistry, University of Southampton, Southampton, SO17 1BJ, UK. M.E.Light@soton.ac.uk., Rhodes MP; School of Chemistry, University of Southampton, Southampton, SO17 1BJ, UK. M.E.Light@soton.ac.uk., Threlfall T; School of Chemistry, University of Southampton, Southampton, SO17 1BJ, UK. M.E.Light@soton.ac.uk., Headen TF; ISIS Neutron and Muon Source, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Didcot, Oxon, UK.
Jazyk: angličtina
Zdroj: Physical chemistry chemical physics : PCCP [Phys Chem Chem Phys] 2023 May 31; Vol. 25 (21), pp. 14898-14906. Date of Electronic Publication: 2023 May 31.
DOI: 10.1039/d3cp01157g
Abstrakt: Through a combination of X-ray and neutron total scattering and Empirical Potential Structure Refinement (EPSR) we explore the prenucleation structures of saturated aqueous magnesium sulfate. The atomistic model we present reveals a system characterised by isolated octahedral aquo magnesium species Mg(H 2 O) 6 , magnesium sulfate pairs (Mg(H 2 O) 5 SO 4 ) and extended clusters built from corner-sharing MgO 6 and SO 4 polyhedra. Many of these features are directly observed in the crystal structures of the known solid form hydrates, including isolated polyhedra, corner sharing chains and rings, and it is only for the extended 3D polyhedral networks of the lower hydrates (mono- & di-) that no proto structures are observed in 2M solution. Looking at the average first solvation shell of the sulfate anion we see a complex and flexible environment that commonly includes water molecules brought into proximity by a coordinated hydrated magnesium. What emerges is a high probability that 10 water molecules will be observed in a combined tetrahedral/octahedral arrangement with a further 7 taking up more dispersed positions giving an average coordination of 17. The tendency for ions to aggregate into clusters allows areas of bulk water to exist that exhibit subtle differences in structure to that of pure water.
Databáze: MEDLINE
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