方阱系统的“真”宽线
The "True" Widom Line for a Square-Well System
摘要：
在本文中，我们提出了范德华模型，它允许一个纯粹的分析研究的流体性质，包括状态方程，相行为和超临界波动。以方势阱系统为例，计算了其液-气相变线和超临界涨落。利用该模型不仅可以计算热力学响应函数（等温压缩率$β_T$、等压热容$C_P$、密度波动$ζ_T$和热膨胀系数$α_T$），还可以计算流体中的相关长度$ξ$。结果表明，束极值迅速扩大后，离开临界点。这样定义的Widom线似乎不能被认为是将超临界区划分为类气区和类液区的真正边界。正如最近所表明的，超临界区相图上的新动态线，即弗伦克尔线，可以用于此目的。
英文摘要：
In the present paper we propose the van der Waals-like model, which allows a purely analytical study of fluid properties including the equation of state, phase behavior and supercritical fluctuations. We take a square-well system as an example and calculate its liquid - gas transition line and supercritical fluctuations. Employing this model allows us to calculate not only the thermodynamic response functions (isothermal compressibility $β_T$, isobaric heat capacity $C_P$, density fluctuations $ζ_T$, and thermal expansion coefficient $α_T$), but also the correlation length in the fluid $ξ$. It is shown that the bunch of extrema widens rapidly upon departure from the critical point. It seems that the Widom line defined in this way cannot be considered as a real boundary that divides the supercritical region into the gaslike and liquidlike regions. As it has been shown recently, the new dynamic line on the phase diagram in the supercritical region, namely the Frenkel line, can be used for this purpose.
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