The relationship between local structure and dynamics is explored for molten sodium carbonate. A flexible fluctuating-charge model, which allows for changes in the shape and charge distribution of the carbonate molecular anion, is developed. The system shows the evolution of highly temperaturedependent complex low-dimensional structures which control the dynamics (and hence the liquid fragility). By varying the molecular anion charge distribution the key interactions responsible for the

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... n of these structures can be identified and rationalised. An increase in the mean charge separation within the carbonate ions increases the connectivity of the emerging structures and leads to an increase in the system fragility.