Uncovering the Atomistic Mechanism for Calcite Step Growth

Calcite crystal modelling at the small scale

30 October 2017

The step-like growth of calcite crystals has been modelled on the atomic level.

Known as ‘limescale’ when it appears on water pipelines and boilers, calcium carbonate or ‘calcite’, is an abundant mineral found in sedimentary rocks. However, due to the many reactions involved, scientists as yet do not have a clear understanding of how it grows so quickly in aqueous environments. A team including researchers from Curtin University used computer simulations to map the conditions under which ions bind to calcite steps in warm water. They found that negatively charged carbonate ions preferentially bind, or ‘adsorb’, at the top edge of existing steps, release energy, and are then joined by the positively charged calcium ions. The formation of ion pairs at an acute step edge enables calcium to move more easily to a site within the crystal that promotes growth.

Accurately mapping the conditions of crystallization could guide the preparation of materials from solution, but further research is required into what limits step size.

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References

1. Angewandte Chemie International Edition 56, 8464–8467 (2017). doi: 10.1002/anie.201701701