Department of Chemistry, University of Utah, Salt Lake City, Utah 84112-0850, USA.
J Chem Phys. 2010 Oct 21;133(15):154516. doi: 10.1063/1.3499323.
The phase behavior of confined water is a topic of intense and current interest due to its relevance in biology, geology, and materials science. Nevertheless, little is known about the phases that water forms even when confined in the simplest geometries, such as water confined between parallel surfaces. Here we use molecular dynamics simulations to compute the phase diagram of two layers of water confined between parallel non hydrogen bonding walls. This study shows that the water bilayer forms a dodecagonal quasicrystal, as well as two previously unreported bilayer crystals, one tiled exclusively by pentagonal rings. Quasicrystals, structures with long-range order but without periodicity, have never before been reported for water. The dodecagonal quasicrystal is obtained from the bilayer liquid through a reversible first-order phase transition and has diffusivity intermediate between that of the bilayer liquid and ice phases. The water quasicrystal and the ice polymorphs based on pentagons are stabilized by compression of the bilayer and are not templated by the confining surfaces, which are smooth. This demonstrates that these novel phases are intrinsically favored in bilayer water and suggests that these structures could be relevant not only for confined water but also for the wetting and properties of water at interfaces.
受限水的相行为是当前生物学、地质学和材料科学领域的研究热点。然而，即使在最简单的几何形状（如平行表面之间的受限水）中，人们对水形成的相也知之甚少。在这里，我们使用分子动力学模拟来计算两层水被平行非氢键壁限制时的相图。这项研究表明，双层水形成了十二面体准晶，以及两种以前未报道的双层晶体，其中一种完全由五边形环组成。准晶是具有长程有序但没有周期性的结构，以前从未在水中报道过。十二面体准晶是通过双层液体的可逆一级相变获得的，扩散率介于双层液体和冰相之间。水的十二面体准晶和基于五边形的冰多晶型体是通过压缩双层稳定的，不受限制表面的影响，这些表面是光滑的。这表明这些新相在双层水中具有内在的优势，并表明这些结构不仅与受限水有关，而且与界面上水的润湿和性质有关。
