The making of bonds during the formation of inorganic solid phases from solution usually follows a series of complex steps. The fact that the emergent species are often structurally nanoparticulate and, in many cases unstable, dictates that they ideally must be characterized not just at length-scales < 100 nm but also as in situ as possible. To this effect, solution-based X-ray scattering methods constitute one of the most versatile tools in studying nanostructured materials as they form.

In this project, we apply the scattering methods: small-angle X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS) and total scattering (with pair distribution function (PDF) analysis) to study the formation and transformation pathways of various mineral phases from solutions. Currently, our research activities are focused of the formation of calcium sulfate (e.g., gypsum, bassanite), phosphates (e.g., struvite) and various aluminosilcates (e.g., saponite). Furthermore, we develop numerical and fundamental mathematical methods for the scattering data modeling and interpretation.

We are advanced users of X-ray producing synchrotron facilities such as Diamond Light Source (UK), European Synchrotron Radiation Facility, ESRF (France), or Deutsches Elektronen-Synchrotron, DESY (Hamburg). Through local collaborations, we have also an access to laboratory-source instruments in the Berlin area.

To unravel the in-depth mechanism of nucleation and growth of hydrated phosphate mineral phases, we performed synchrotron-based experiments in December 2022 at Diamond Light Source (UK) at I22 beam line, to follow their time-resolved formation via in-situ SAXS/WAXS, at different supersaturations and environmentally relevant temperatures. We could model the kinetics of  crystal growth at various temperatures to derive the mechanism of growth and activation energy of these minerals. Our results provided new insights on these crystallization kinetics of these minerals and their impact on phosphate nutrient cycling in these systems.

(authors from the group in bold)

Besselink, R., Stawski, T.M., Freeman, H.M., Hövelmann, J., Tobler, D.J., Benning, L.G. (2020). Mechanism of saponite crystallization from a rapidly formed amorphous intermediate. Crystal Growth & Design, 20, 5, 3365-3373. DOI: 10.1021/acs.cgd.0c00151.

Stawski, T.M., Besselink, R., Chatzipanagis, K., Hövelmann, J., Benning, L.G., Van Driessche, A.E.S (2020). Nucleation pathway of calcium sulfate hemihydrate (bassanite) from solution: implications for calcium sulfates on Mars. The Journal of Physical Chemistry C. DOI: 10.1021/acs.jpcc.0c01041.

Hövelmann, J., Stawski, T., Freeman, H., Besselink, R., Mayanna, S., Perez, J.P.H., Hondow, N.S., Benning, L.G. (2019). Struvite crystallisation and the effect of Co2+ ions. Minerals, 9, 9, 503. DOI: 10.3390/min9090503.

Stawski, T., Freeman, H., Van Driessche, A.E.S., Hövelmann, J., Besselink, R., Wirth, R., Benning, L. G. (2019). Particle-mediated nucleation pathways are imprinted in the internal structure of calcium sulfate single crystals. Crystal Growth and Design, 19, 7, 3714-3721. DOI: 10.1021/acs.cgd.9b00066.

Stawski, T., Van Driessche, A.E.S., Besselink, R., Byrne, E.H., Raiteri, P., Gale, J.D., Benning, L.G. (2019). The structure of CaSO4 nanorods: The precursor of gypsum. The Journal of Physical Chemistry C, 123, 37, 23151-23158. DOI: 10.1021/acs.jpcc.9b04268.

Matamoros-Veloza, A., Stawski, T., & Benning, L.G. (2018). Nanoparticle assembly leads to mackinawite formation. Crystal Growth and Design, 18, 11, 6757-6764. DOI: 10.1021/acs.cgd.8b01025.