Del Rosso Leonardo, Celli Milva, Grazzi Francesco, Catti Michele, Hansen Thomas C, Fortes A Dominic, Ulivi Lorenzo
Consiglio Nazionale delle Ricerche, Istituto di Fisica Applicata 'Nello Carrara', Sesto Fiorentino, Italy.
Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, Milano, Italy.
Nat Mater. 2020 Jun;19(6):663-668. doi: 10.1038/s41563-020-0606-y. Epub 2020 Feb 3.
Amongst the more than 18 different forms of water ice, only the common hexagonal phase and the cubic phase are present in nature on Earth. Nonetheless, it is now widely recognized that all samples of 'cubic ice' discovered so far do not have a fully cubic crystal structure but instead are stacking-disordered forms of ice I (namely, ice Isd), which contain both hexagonal and cubic stacking sequences of hydrogen-bonded water molecules. Here, we describe a method to obtain large quantities of cubic ice Ic with high structural purity. Cubic ice Ic is formed by heating a powder of DO ice XVII obtained from annealing of pristine C hydrate samples under dynamic vacuum. Neutron diffraction experiments performed on two different instruments and Raman spectroscopy measurements confirm the structural purity of the cubic ice, Ic. These findings contribute to a better understanding of ice I polymorphism and the existence of the two natural ice forms.
在18种以上不同形式的水冰中，地球上自然界中仅存在常见的六方相和立方相。然而，目前人们普遍认识到，迄今为止发现的所有“立方冰”样品都不具有完全的立方晶体结构，而是冰I的堆垛无序形式（即冰Isd），其中包含氢键水分子的六方和立方堆垛序列。在此，我们描述了一种获得大量具有高结构纯度的立方冰Ic的方法。立方冰Ic是通过加热在动态真空下对原始C水合物样品进行退火得到的DO冰XVII粉末而形成的。在两种不同仪器上进行的中子衍射实验和拉曼光谱测量证实了立方冰Ic的结构纯度。这些发现有助于更好地理解冰I的多晶型现象以及两种天然冰形式的存在。
