Abstract
Formation of calcium carbonate and its hydrates are important for a wide variety of geological, biological, and technological concerns. Recent studies have determined that formation of anhydrous crystalline calcite, aragonite, and vaterite can involve a complex series of nonclassical pathways in which the hydrated polymorphs monohydrocalcite (CaCO3·H2O), ikaite (CaCO3·6H2O), and amorphous calcium carbonate (ACC) play key roles and in some instances are stable or metastable endproducts. The stages of nucleation and crystallization along these pathways are not well understood, nor is how what is learned in an aqueous environment transfers to CO2-rich conditions. In this work ab initio thermodynamics based on density-functional theory and experimental chemical potentials for H2O-rich and CO2-rich systems are used to determine the stability of calcium carbonate polymorphs as a function of environmental conditions. In water-saturated supercritical CO2, formation of ikaite and monohydrocalcite are both highly e...
Published Version
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