Franzese G, Malescio G, Skibinsky A, Buldyrev S V, Stanley H E
Center for Polymer Studies and Department of Physics, Boston University, Massachusetts 02215, USA.
Nature. 2001 Feb 8;409(6821):692-5. doi: 10.1038/35055514.
Recent experimental results indicate that phosphorus--a single-component system--can have a high-density liquid (HDL) and a low-density liquid (LDL) phase. A first-order transition between two liquids of different densities is consistent with experimental data for a variety of materials, including single-component systems such as water, silica and carbon. Molecular dynamics simulations of very specific models for supercooled water, liquid carbon and supercooled silica predict a LDL-HDL critical point, but a coherent and general interpretation of the LDL-HDL transition is lacking. Here we show that the presence of a LDL and a HDL can be directly related to an interaction potential with an attractive part and two characteristic short-range repulsive distances. This kind of interaction is common to other single-component materials in the liquid state (in particular, liquid metals), and such potentials are often used to describe systems that exhibit a density anomaly. However, our results show that the LDL and HDL phases can occur in systems with no density anomaly. Our results therefore present an experimental challenge to uncover a liquid-liquid transition in systems like liquid metals, regardless of the presence of a density anomaly.
近期的实验结果表明，磷（一种单组分体系）能够存在高密度液相（HDL）和低密度液相（LDL）相。不同密度的两种液体之间的一级相变与包括水、二氧化硅和碳等单组分体系在内的多种材料的实验数据相符。对过冷水、液态碳和过冷二氧化硅的特定模型进行的分子动力学模拟预测了一个LDL-HDL临界点，但目前缺乏对LDL-HDL转变的连贯且通用的解释。在此我们表明，LDL和HDL的存在可直接与具有吸引部分以及两个特征性短程排斥距离的相互作用势相关。这种相互作用在其他液态单组分材料（特别是液态金属）中很常见，并且此类势通常用于描述呈现密度反常的体系。然而，我们的结果表明，LDL和HDL相可出现在不存在密度反常的体系中。因此，我们的结果对在液态金属等体系中揭示液-液转变提出了一项实验挑战，无论是否存在密度反常。
