CRYSTAL CLEAR: determining the impact of charge on crystal nucleation

ended

All of the crystals that form in water on Earth are formed through reaction between oppositely charged ions. In these crystals, the ions are present in an ideal, charge-balanced ionic ratio. In contrast, the natural solutions in which they form, contain widely diverging ionic ratios. When crystals nucleate from natural solutions, they will be charged, and charge has a massive impact on the behaviour of small new crystals. Most nucleation experiments have been conducted in solutions with charge-balanced ionic ratios. This leads to uncharged crystal formation, which can be described with nucleation theories based on uncharged gas condensation into droplets. My pilot data show that this does not apply when ionic ratios diverge. New crystals then form and grow much slower than expected. Similarly, in natural solutions, crystals are often expected to form, but they do not, and vice versa. Clearly, we still have no idea how, why and how fast crystals nucleate in Earth surface environments. In this project, I will test the hypothesis that ionic ratio has a dramatic impact on nucleation: crystals will be charged, and this charge will determine their size, how and how fast they grow, aggregate, and transform. I will conduct state-of-the-art experiments and analyses that will provide in situ knowledge of the impact of ionic ratio on the charge, size, growth, aggregation and transformation of nuclei. Experiments will be complemented with advanced modelling to derive charged-nuclei stability and surrounding water properties. The results will be assimilated in a new crystal nucleation theory. CRYSTAL CLEAR will focus on barite, calcite and pyrite as examples of highly relevant Earth Materials. The outcome will be improved geoengineering options such as drinking water production and CO2 sequestration. My project will bring a new vision on crystal formation in nature, with radically improved predictions of rates and mechanisms, and a paradigm shift in nucleation theory.