Free energy and structure of calcium carbonate nanoparticles during early stages of crystallization.
We introduce a metadynamics based scheme for computing the free energy of nanoparticles as a function of their crystalline order. The method is applied to small nanoparticles of the biomineral calcium carbonate to determine the preferred structure during early stages of crystal growth. For particles 2 nm in diameter, we establish a large energetic preference for amorphous particle morphologies. Particles with partial crystalline order consistent with vaterite are also observed with substantially lower probability. The absence of the stable calcite phase and stability of the amorphous state support recent conjectures that calcite formation starts via the deposition of amorphous calcium carbonate.
Department of Chemistry and Centre for Scientific Computing, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, United Kingdom. d.quigley@warwick.ac.uk
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D002119:Calcium Carbonate / Q000737:chemistry*; D003460:Crystallization; D008903:Minerals / Q000737:chemistry; D008958:Models, Molecular; D053758:Nanoparticles / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D013816:Thermodynamics
D008903:Minerals; D012997:Solvents; D002119:Calcium Carbonate