Hamp Rachael E, Salzmann Christoph G, Amato Zachary, Beaumont Milz L, Chinnery Hannah E, Fawdon Peter, Headen Thomas F, Henry Paul F, Perera Liam, Thompson Stephen P, Fox-Powell Mark G
AstrobiologyOU, School of Environment, Earth and Ecosystem Sciences, Open University, Walton Hall, Milton Keynes MK7 6AA, United Kingdom.
Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom.
J Phys Chem Lett. 2024 Dec 19;15(50):12301-12308. doi: 10.1021/acs.jpclett.4c02752. Epub 2024 Dec 5.
Sodium chloride (NaCl) plays an important role in geochemistry, biology, industry, and food production, and it is among the most common salts in the solar system. Here, we report the discovery of a metastable NaCl dihydrate formed through rapid freezing (10-10 K s) of a NaCl solution at ambient pressure. Using synchrotron X-ray and neutron powder diffraction, we show that it transforms irreversibly to hydrohalite and ice Ih above 190 K upon heating and propose it is structurally related to hydrohalite with a 3 × 1 × 3 supercell as its unit cell. Calorimetric analyses reveal that the new hydrate transforms to hydrohalite with a heat release of -3.47 ± 0.55 kJ mol. The identification of this new NaCl dihydrate on the surfaces of icy worlds such as the moons of Jupiter and Saturn could indicate regions of recent activity where subsurface brines have frozen rapidly, priority targets for upcoming planetary missions.
氯化钠（NaCl）在地球化学、生物学、工业和食品生产中发挥着重要作用，并且是太阳系中最常见的盐类之一。在此，我们报告了在常压下通过快速冷冻（10⁻¹⁰ K s⁻¹）氯化钠溶液形成的一种亚稳态二水合氯化钠的发现。利用同步加速器X射线和中子粉末衍射，我们表明，加热时它在190 K以上不可逆地转变为水氯镁石和冰Ih，并提出它在结构上与水氯镁石相关，其晶胞为3×1×3超晶胞。量热分析表明，这种新水合物转变为水氯镁石时放热-3.47±0.55 kJ mol⁻¹。在木星和土星卫星等冰冻星球表面发现这种新的二水合氯化钠，可能表明存在近期活动区域，即地下物质快速冻结的区域，这是即将进行的行星任务的优先目标。
