Departamento de Física, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil.
J Chem Phys. 2013 Apr 28;138(16):164502. doi: 10.1063/1.4802006.
Three core-softened families of potentials are checked for the presence of density and diffusion anomalies. These potentials exhibit a repulsive core with a softening region and at larger distances an attractive well. We found that the region in the pressure-temperature phase diagram in which the anomalies are present increases if the slope between the core-softened scale and the attractive part of the potential decreases. The anomalous region also increases if the range of the core-softened or of the attractive part of the potential decreases. We also show that the presence of the density anomaly is consistent with the non-monotonic changes of the radial distribution function at each one of the two scales when temperature and density are varied. Then, using this anomalous behavior of the structure we show that the pressure and the temperature at which the radial distribution function of one of the two length scales equals the radial distribution function of the other length scales identify the Widom line.
检查了三个核心软化势家族的位势，以确定密度和扩散异常的存在。这些位势表现出一个具有软化区域的排斥核，在较大距离处具有吸引力的阱。我们发现，如果核心软化标度和位势的吸引力部分之间的斜率减小，那么在压力-温度相图中存在异常的区域会增加。如果核心软化或位势吸引力部分的范围减小，异常区域也会增加。我们还表明，密度异常的存在与在温度和密度变化时，两个标度中每一个的径向分布函数的非单调变化一致。然后，利用这种结构的异常行为，我们表明，当两个长度标度中的一个的径向分布函数等于另一个长度标度的径向分布函数时，压力和温度确定 Widom 线。
