Instituto de Física, Universidade Federal do Rio Grande do Sul, 91501-970, Porto Alegre, RS, Brazil.
J Chem Phys. 2011 Sep 14;135(10):104507. doi: 10.1063/1.3630941.
Using molecular dynamic simulations, we study three families of continuous core-softened potentials consisting of two length scales: a shoulder scale and an attractive scale. All the families have the same slope between the two length scales but exhibit different potential energy gap between them. For each family three shoulder depths are analyzed. We show that all these systems exhibit a liquid-liquid phase transition between a high density liquid phase and a low density liquid phase ending at a critical point. The critical temperature is the same for all cases suggesting that the critical temperature is only dependent on the slope between the two scales. The critical pressure decreases with the decrease of the potential energy gap between the two scales suggesting that the pressure is responsible for forming the high density liquid. We also show, using the radial distribution function and the excess entropy analysis, that the density, the diffusion, and the structural anomalies are present if particles move from the attractive scale to the shoulder scale with the increase of the temperature indicating that the anomalous behavior depends only in what happens up to the second coordination shell.
使用分子动力学模拟，我们研究了三种由两个长度尺度组成的连续核软化势家族：一个肩部尺度和一个吸引尺度。所有家族在这两个长度尺度之间都具有相同的斜率，但它们之间的势能间隙不同。对于每个家族，我们分析了三个肩部深度。我们表明，所有这些系统都表现出高密液相和低密液相之间的液-液相转变，最终在临界点结束。所有情况下的临界温度相同，这表明临界温度仅取决于两个尺度之间的斜率。临界压力随两个尺度之间的势能间隙的减小而减小，这表明压力负责形成高密度液体。我们还通过径向分布函数和过剩熵分析表明，如果粒子随着温度的升高从吸引尺度移动到肩部尺度，密度、扩散和结构异常会出现，这表明异常行为仅取决于直到第二个配位壳层发生的情况。
