Editorial for Special Issue “Nucleation of Minerals: Precursors, Intermediates and Their Use in Materials Chemistry”

Abstract

Nucleation is the key event in mineralization, but a general molecular understanding of phase separation mechanisms is still missing, despite more than 100 years of research in this field [1]. In the recent years, many studies have highlighted the occurrence of precursors and intermediates, which seem to challenge the assumptions underlying classical theories of nucleation and growth. This is especially true for the field of biomineralization, where bio-inspired strategies take advantage of the precursors' and intermediates' special properties for the generation of advanced materials. All of this has led to the development of "non-classical" frameworks, which, however, often lack quantitative expressions for the evaluation and prediction of phase separation, growth and ripening processes, and are under considerable debate. It is, thus, evident that there is a crucial need for research into the early stages of mineral nucleation and growth, designed for the testing, refinement and expansion of the different existing notions. This special issue of Minerals aimed to bring together corresponding studies from all these areas, dealing with precursors and intermediates in mineralization with the hope that it may contribute to the achievement of a better understanding of nucleation precursors and intermediates, and their target-oriented use in materials chemistry.In his commentary, Evans [2] summarises different existing nucleation theories and discusses them from the point of view of biomineralization. The focus lies on proteins and their role in mineral precursor formation, stabilisation, and assembly into crystalline polymorphs. It is stressed that a limitation of the advancement of the understanding of protein-controlled mineralization processes [3] is, at least, partly due to variations in techniques, methodologies and the lack of standardisation in mineral assay experimentation. Evans argues that the protein community should adopt standardized nucleation assays [4,5], allowing for cross-comparisons and kinetic observations. Burgos-Cara et al. [6] use such an experimental approach for studying the effects of background ionic species on the formation and stability of CaCO 3 pre-nucleation species in aqueous solutions. They find that the effective critical supersaturation in the presence of background ions with a decreasing ionic radius becomes systematically higher, and propose that the stabilisation of hydration water molecules impedes dehydration processes, which are essential steps during mineral precipitation, according to the notions of the so-called pre-nucleation cluster pathway [1].Several papers of this Minerals special issue address further methodological aspects associated with research into mineral nucleation and growth. The contribution of Kröger and Verch [7] deals with studies employing liquid cell transmission electron microscopy (LCTEM). 2D finite element simulations highlight that the confinement, which occurs in typical LCTEM cells and can significantly reduce the concentration of available ions, c...

Metal film growth on weakly-interacting substrates : Multiscale modeling

“…Nucleation is an universal process that triggers an ample variety of natural phenomena, including droplet formation in clouds [72], ice crystallization in water [73], or mineral growth under the Earth crust [74]. Within the field of film growth, nucleation plays an important role as it does not only determines the initial distribution of islands on the substrate, but also controls the CHAPTER 2.…”