Zhaoyong Zou, W. Habraken, G. Matveeva
Jan 25, 2019
Citations
1
Influential Citations
125
Citations
Quality indicators
Journal
Science
Abstract
Hydrous CaCO3 gets a new structure Calcium carbonate (CaCO3) forms important minerals on Earth and is a model system for understanding crystal nucleation. Three different structures of CaCO3 are known, along with two structures that are hydrated. Zou et al. found a third hydrated CaCO3 structure formed from amorphous CaCO3 in the presence of magnesium ions. The discovery illustrates the importance of amorphous precursors for producing new materials. Science, this issue p. 396 Hydrous calcium carbonate with a new crystal structure can be synthesized from the amorphous form in an aqueous solution. As one of the most abundant materials in the world, calcium carbonate, CaCO3, is the main constituent of the skeletons and shells of various marine organisms. It is used in the cement industry and plays a crucial role in the global carbon cycle and formation of sedimentary rocks. For more than a century, only three polymorphs of pure CaCO3—calcite, aragonite, and vaterite—were known to exist at ambient conditions, as well as two hydrated crystal phases, monohydrocalcite (CaCO3·1H2O) and ikaite (CaCO3·6H2O). While investigating the role of magnesium ions in crystallization pathways of amorphous calcium carbonate, we unexpectedly discovered an unknown crystalline phase, hemihydrate CaCO3·½H2O, with monoclinic structure. This discovery may have important implications in biomineralization, geology, and industrial processes based on hydration of CaCO3.