Geometrically-frustrated interactions drive structural complexity in amorphous calcium carbonate

• DOI: 10.48550/arxiv.2303.06178
• Publication Date: 2023-01-01
• Authors: Thomas C. Nicholas; Adam E. Stones; Adam Patel; F. Marc Michel; Richard J. Reeder; Dirk G. A. L. Aarts; Volker L. Deringer; Andrew L. Goodwin
• Keywords: Metastability; Amorphous calcium carbonate

Amorphous calcium carbonate (ACC) is an important precursor for biomineralisation in marine organisms. Among the key outstanding problems regarding ACC are how best to understand its structure and rationalise metastability as amorphous phase. Here, we report high-quality atomistic models of generated by using state-of-the-art interatomic potentials help guide fits X-ray total scattering data. Exploiting a recently-developed inversion approach, extract from these effective Ca$\boldsymbol\cdots$Ca interaction potential governing formation. This contains minima at two competing distances, corresponding different ways which ions bridge Ca$^{2+}$-ion pairs. We reveal unexpected mapping Lennard-Jones--Gauss (LJG) model normally studied context computational soft-matter, with empirical LJG parameters taking values known promote structural complexity. In this way show that both complex resilience crystallisation actually encoded geometrically-frustrated interactions between Ca$^{\boldsymbol 2+}$ ions.