Adsorption, Diffusion and Structure Formation of Water on Calcite: Fundamental Processes in Wetting of an Omnipresent Mineral Surface

表面的水在自然界和科技中无处不在。因此，固-水界面在包括地球化学、环境化学以及催化在内的广泛领域中起着至关重要的作用。在这种背景下，表面成核是一个特别有趣的现象，它已经被研究了几个世纪。然而，许多关于表面水吸附和结构形成的物理化学机制的基本问题仍然没有得到很好的理解。方解石是研究水成核现象的一个特别有趣的底物，因为它代表了地球上最丰富的碳酸盐。它在许多日常生活和工业过程中发挥着重要作用，包括各种领域，如阻垢、石油回收或建筑。尽管方解石-水界面很重要，但人们对水在该表面上的吸附、扩散和结构形成的分子级细节知之甚少。这种信息的缺乏主要是因为方解石是一种电绝缘材料，对经典的表面科学技术来说是一个重大挑战。在这方面，在超高真空中进行的动态原子力显微镜已被证明是一种理想的在块状绝缘子表面获得原子分辨率的技术。该项目的目标是揭示在超高真空中保持的方解石(10.4)的天然解理面上水的吸附、扩散和结构形成的基本步骤。我们将确定水吸附的基本参数，如吸附自由能和吸附熵，以及水单体扩散势垒。为了阐明依赖温度的水结构的形成，我们将研究水团簇的形成和扩散，以及依赖于温度的单层和多层生长。我们计划用轻水(H2O)和重水(D2O)进行实验，以揭示氢键在这些结构中的影响。综上所述，该项目旨在通过记录低温和可变温度下的AFM数据，阐明水在方解石(10.4)上吸附、扩散以及结构形成和生长的基本物理机制。这些见解有望为理解水-方解石界面在广泛不同地区的反应性提供重要的基本信息。

Water at surfaces is omnipresent both in nature and technology. Therefore, solid-water interfaces are pivotal in a broad range of fields, including, e.g., geochemistry, environmental chemistry as well as catalysis. Ice nucleation at surfaces is a particularly interesting phenomenon in this context, which has been studied since centuries. Yet, many fundamental questions regarding the physico-chemical mechanisms responsible for water adsorption and structure formation at surfaces remain poorly understood.Calcite is a particularly interesting substrate to study water nucleation phenomena, since it represents the most abundant carbonate on earth. It plays a major role in many every day's life and industrial processes, including such diverse fields as scale inhibition, oil recovery, or construction. Despite the importance of the calcite-water interface, very little is known about the molecular-scale details of water adsorption, diffusion and structure formation on this surface. This lack of information is mostly due to the fact that calcite, being an electrically insulating material, represents a major challenge for classical surface science techniques. In this respect, dynamic atomic force microscopy carried out in ultra-high vacuum has proven to constitute an ideally suited technique to obtain atomic resolution on bulk insulator surfaces.The goal of the project is unravelling fundamental steps in water adsorption, diffusion and structure formation on the natural cleavage plane of calcite, namely calcite (10.4), kept in ultra-high vacuum. We will determine basic parameters in water adsorption such as free energy and entropy of adsorption as well as water monomer diffusion barriers. To elucidate temperature-dependent water structure formation, we will study water cluster formation and diffusion as well as temperature-dependent mono- and multilayer growth. Experiments with both light (H2O) and heavy (D2O) water are planned to shed light onto the influence of hydrogen bonding in these structures.In summary, the project aims at elucidating the basic physical mechanisms in water adsorption, diffusion as well as structure formation and growth on calcite (10.4) by recording AFM data at low and variable temperatures. These insights are expected to provide important fundamental input for understanding the reactivity of water-calcite interfaces in a broad range of different areas.