Institute for High Pressure Physics, Russian Academy of Sciences, Troitsk 142190, Moscow Region, Russia.
J Chem Phys. 2011 Sep 28;135(12):124512. doi: 10.1063/1.3643115.
In the present article we carry out a molecular dynamics study of the core-softened system and show that the existence of the water-like anomalies in this system depends on the trajectory in P-ρ-T space along which the behavior of the system is studied. For example, diffusion and structural anomalies are visible along isotherms as a function of density, but disappears along the isochores and isobars as a function of temperature. On the other hand, the diffusion anomaly may be seen along adiabats as a function of temperature, density, and pressure. It should be noted that it may be no signature of a particular anomaly along a particular trajectory, but the anomalous region for that particular anomaly can be defined when all possible trajectories in the same space are examined (for example, signature of diffusion anomaly is evident through the crossing of different isochors. However, there is no signature of diffusion anomaly along a particular isochor). We also analyze the applicability of the Rosenfeld entropy scaling relations to this system in the regions with the water-like anomalies. It is shown that the validity of the Rosenfeld scaling relation for the diffusion coefficient also depends on the trajectory in the P-ρ-T space along which the kinetic coefficients and the excess entropy are calculated.
在本文中，我们进行了核心软化系统的分子动力学研究，结果表明，该系统中存在类似水的异常现象取决于在 P-ρ-T 空间中沿着研究系统行为的轨迹。例如，扩散和结构异常可以沿着等密度线作为密度的函数显现，但沿着等压和等容线作为温度的函数消失。另一方面，扩散异常可以沿着绝热线作为温度、密度和压力的函数显现。应当指出的是，沿着特定轨迹可能没有特定异常的特征，但当在相同空间中检查所有可能的轨迹时，可以定义特定异常的异常区域（例如，通过不同等容线的交叉可以明显看出扩散异常的特征。然而，沿着特定等容线没有扩散异常的特征）。我们还分析了该系统在类似水的异常区域中罗森菲尔德熵标度关系的适用性。结果表明，扩散系数的罗森菲尔德标度关系的有效性也取决于在 P-ρ-T 空间中沿着计算动力学系数和过剩熵的轨迹。
