Wednesday 23rd July

12 – 1 pm

Rm 312.222

Paolo Raiteri

Department of Chemistry and Nanochemistry Research Institute
Curtin University, Perth WA

On the existence of prenucleation clusters of alkaline earth carbonates

Abstract

Calcium carbonate (CaCO3) is arguably the most studied mineral because of its importance in industrial applications, geo-sequestration and bio-mineralisation. Despite this global interest a full understanding of the molecular mechanisms that control the nucleation and growth of CaCO3 is still elusive. Thanks to the constant increase of computational power, atomistic simulations have become an invaluable tool to help interpret the experimental results and we are now at a stage where computer simulations can make reliable predictions in areas not yet achievable by experiments.

In recent years the appearance of calcium carbonate stable clusters and of a dense liquid phase before the onset of nucleation has been proposed and verified, both experimentally and computationally [1-3]. This has led to a new picture of the formation pathway of carbonate minerals emerging. Initially, the ions aggregate to form dynamic chain like structures [1,2] (DOLLOP) that, upon increase in the ion activities, undergo a liquid-liquid phase separation to form a dense liquid phase [3]. This dense liquid phase progressively looses water and precipitates in the form of amorphous calcium carbonate, which eventually transforms into one of the commonly found anhydrous polymorphs.

This phenomenon is believed not to be limited to calcium carbonate, but to be a general growth mechanism for the formation of many minerals [4], such as the other alkaline earth carbonates, sulphates and phosphates. Here large-scale computer simulations can provide a unique opportunity to test this hypothesis. A carefully parameterised force field, which was calibrated against the thermodynamics of the species in solution and in the crystalline phases [5], has indeed been already used to study this very phenomenon for the calcium carbonate system [2,3].

[1] Gebauer et. al. (2008) Science. 322, 1819-1822.

[2] Demichelis et. al. (2011) Nat. Commun. 2, 590.

[3] Wallace et. al. (2013) Science, 341, 885-889.

[4] Gebauer et. al. (2014) Chem. Soc. Rev., DOI: 10.1039/C3CS60451A.

[5] Raiteri, et al. (2010) J. Phys. Chem. C, 114, 5997- 6010.

Biography

Dr Paolo Raiteri obtained his MSc and PhD in Material Science from the University of Milano-Bicocca in 1999 and 2003, respectively. Successively he became a post-doctoral research assistant in the group of Prof Parrinello at ETH Zurich, who is a world leader in the field of Computational Chemistry. In 2008 Dr Raiteri moved to Curtin as an Early Career Research Fellow and in 2009 he became an ARC Research Fellow (ARF). From January 2014 Dr Raiteri is an ARC Future Fellow and Senior Research Fellow at Curtin University. Dr Raiteri has so far published 59 papers in peered-reviewed journals, including Science, Nature and Nature Communications and a WoS h-index of 19.