Ligth water, heavy water, and sodium chloride aqueous solutions under extreme conditions to shed light on water anomalies and structural properties

极端条件下的轻水、重水和氯化钠水溶液，以揭示水的异常和结构特性

• 批准号: 431324570
• 负责人: Dr. Christian Sternemann
• 金额: --
• 依托单位: Plateforme Ingénierie spatiale, Images et Géomatique (ISIG)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/431324570?language=en
• 关键词: Ligth; water; heavy; sodium; chloride

Water and aqueous solutions are ubiquitous, being involved in countless natural phenomena and technological processes. Water stands out among all liquids because of its numerous physical anomalies related to its complex hydrogen bond network, yet it is not fully understood. The goal of our project is to combine the efforts of researchers in physics and geosciences to gain new knowledge about water and aqueous solutions under extreme conditions. On the one hand, we will explore the stretched liquid state, at negative pressures. The liquid is then metastable with respect to vapor and a bubble may nucleate at any time, bringing back the system to equilibrium. But small liquid droplets trapped in a quartz matrix reach beyond –100 MPa in the metastable state and can be studied with photons. We will use Brillouin, visible Raman and x-ray Raman spectroscopy in order to elucidate the thermodynamics and molecular structure of stretched water. Experiments will be performed not only on stretched ordinary water but also on stretched heavy water and aqueous NaCl solutions, as they are predicted to grant access to specific features, which cannot be found in ordinary water. Specifically, the line of density maxima of heavy water is predicted to reach a maximum temperature at a negative pressure accessible to experiment, while the line of compressibility maxima recentlyfound in pure, stretched water is predicted to become more pronounced with a low salt concentration. Confirming or not these features will have broad implications for our understanding of water and its phase diagram, including the intriguing (debated) possibility of liquid polyamorphism – the existence of two distinct liquid phases of water. On the other hand, we will study the stable fluid state under high pressure and temperature conditions. One key property of water in geological processes (e.g. subduction zones and hydrothermal activity) is viscosity. Yet, surprisingly, data is scarce for pure water at high pressure, and absent for salty water. Moreover, the current measurement technique (rolling ball viscometer inside the small chamber of a diamond anvil cell) has limitations and may suffer from bias. We will implement a new technique based on the Brownian motion of spheres of ca. 100 nm diameter to bypass these limitations. These results will be directly linked to the molecular structure using visible Raman spectroscopy. For further insight, we will use x-ray Raman scattering spectroscopy, particularly to address the less well known structure of heavy water and NaCl solutions at conditions up to near the liquid-vapor critical point, assessing the influence on ion hydration. Herewith, we combine our complementary expertise in order to study water, heavy water, and aqueous NaCl solutions at extreme conditions, in the stretched, supercritical and high-density regimes, giving rise to a deeper understanding of the microscopic structure of the fluids and their relation to macroscopic properties.

水和水溶液无处不在，涉及无数的自然现象和技术过程。水在所有液体中脱颖而出，因为它有许多与其复杂的氢键网络有关的物理异常，但它还没有被完全理解。我们项目的目标是联合收割机结合物理学和地球科学研究人员的努力，获得关于极端条件下水和水溶液的新知识。一方面，我们将探索在负压下的拉伸液态。然后，液体相对于蒸气是亚稳态的，并且气泡可以在任何时候成核，使系统恢复平衡。但是被捕获在石英基质中的小液滴在亚稳态下达到超过-100 MPa，并且可以用光子进行研究。我们将使用布里渊，可见拉曼和X-射线拉曼光谱，以阐明热力学和拉伸水的分子结构。实验不仅将在拉伸的普通水上进行，而且还将在拉伸的重水和NaCl水溶液上进行，因为预计它们将获得在普通水中无法找到的特定功能。具体地说，重水的密度最大值线预计将达到一个最高温度，在一个负压接近实验，而最近发现的压缩性最大值线在纯，拉伸水预计将变得更加明显与低盐浓度。无论是否描述这些特征，都将对我们理解水及其相图产生广泛的影响，包括液体多晶性的可能性-存在两种不同的液相水。另一方面，我们将研究高温高压条件下的稳定流体状态。水在地质过程（例如俯冲带和热液活动）中的一个关键特性是粘度。然而，令人惊讶的是，高压下纯水的数据很少，盐水的数据也不存在。此外，目前的测量技术（金刚石砧座小室内的滚珠粘度计）具有局限性，并且可能受到偏差的影响。我们将实现一个新的技术的基础上的布朗运动的领域约。100 nm直径，以绕过这些限制。这些结果将直接链接到分子结构使用可见拉曼光谱。为了进一步了解，我们将使用X-射线拉曼散射光谱，特别是要解决不太知名的结构，重水和NaCl溶液的条件下接近液-汽临界点，评估离子水合的影响。因此，我们联合收割机结合我们的互补专业知识，以研究水，重水和NaCl水溶液在极端条件下，在拉伸，超临界和高密度制度，从而引起更深入地了解流体的微观结构及其与宏观性质的关系。