Yagasaki Takuma, Matsumoto Masakazu, Tanaka Hideki
Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan.
J Chem Phys. 2019 Jun 7;150(21):214506. doi: 10.1063/1.5096429.
In the liquid-liquid phase transition scenario, supercooled water separates into the high density liquid (HDL) and low density liquid (LDL) phases at temperatures lower than the second critical point. We investigate the effects of hydrophilic and hydrophobic solutes on the liquid-liquid phase transition using molecular dynamics simulations. It is found that a supercooled aqueous NaCl solution separates into solute-rich HDL and solute-poor LDL parts at low pressures. By contrast, a supercooled aqueous Ne solution separates into solute-rich LDL and solute-poor HDL parts at high pressures. Both the solutes increase the high temperature limit of the liquid-liquid separation. The degree of separation is quantified using the local density of solute particles to determine the liquid-liquid coexistence region in the pressure-temperature phase diagram. The effects of NaCl and Ne on the phase diagram of supercooled water are explained in terms of preferential solvation of ions in HDL and that of small hydrophobic particles in LDL, respectively.
在液-液相转变的情况下，过冷水在低于第二临界点的温度下会分离成高密度液体（HDL）和低密度液体（LDL）相。我们使用分子动力学模拟研究亲水性和疏水性溶质对液-液相转变的影响。研究发现，过冷的NaCl水溶液在低压下会分离成富含溶质的HDL和贫溶质的LDL部分。相比之下，过冷的Ne水溶液在高压下会分离成富含溶质的LDL和贫溶质的HDL部分。两种溶质都会提高液-液分离的高温极限。使用溶质颗粒的局部密度来量化分离程度，以确定压力-温度相图中的液-液共存区域。NaCl和Ne对过冷水相图的影响分别根据HDL中离子的优先溶剂化和LDL中小疏水颗粒的优先溶剂化来解释。
