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Ion Pairing and Multiple Ion Binding in Calcium Carbonate Solutions Based on a Polarizable AMOEBA Force Field and Ab Initio Molecular Dynamics

preprint
revised on 31.03.2020 and posted on 02.04.2020 by Paolo Raiteri, Alicia Schuitemaker, Julian Gale
The speciation of calcium carbonate in water is important to the geochemistry of the world’s oceans and has ignited significant debate regarding the mechanism by which nucleation occurs. Here it is vital to be able to quantify the thermodynamics of ion pairing versus higher order association processes in order to distinguish between possible pathways. Given that it is experimentally challenging to quantify such species, here we determine the thermodynamics for ion pairing and multiple binding of calcium carbonate species using bias-enhanced molecular dynamics. In order to examine the uncertainties underlying these results, we have derived a new polarizable force field for both calcium carbonate and bicarbonate in water based on the AMOEBA model to compare against our earlier rigid-ion model, both of which are further benchmarked against ab initio molecular dynamics for the ion pair. Both force fields consistently indicate that the association of calcium carbonate ion pairs is stable, though with an equilibrium constant that is lower than for ion pairing itself.

Funding

Australian Research Council (FT130100463)

Australian Research Council (FL180100087)

History

Email Address of Submitting Author

p.raiteri@curtin.edu.au

Institution

Curtin University

Country

Australia

ORCID For Submitting Author

0000-0003-0692-0505

Declaration of Conflict of Interest

No competing conflict of interest

Version Notes

First revision

Exports