Volume shifts are commonly applied to cubic equations of state (EoS) to improve the description of densities, since they do not affect the phase equilibria. This concept can in principle be extended to any other EoS, but studies using this approach are scarce for EoS based on perturbation theory, mainly because most of these equations already provide accurate liquid density results. However, as with cubic EoS, most statistical associating fluid theory (SAFT) type EoS have difficulties in describing derivative properties, more noticeably the speed of sound. In this work, we study the use of a volume shift in perturbed-chain statistical associating fluid theory (PC-SAFT). A new parametrization procedure is proposed that involves the use of vapor pressure, the pressure derivative with respect to density obtained from isothermal compressibility, and molar volume data. This last property is only applied to fit a constant Péneloux-type volume shift. It is shown that this approach provides a good description of saturation pressures and liquid densities, as well as an improved description of the speed of sound. The impact of these changes on the performance of PC-SAFT in the description of properties and phase equilibria is further investigated by comparing the results of this methodology with those obtained with the available PC-SAFT parameter sets.

中文翻译：

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在扰动链统计关联流体理论中使用体积偏移来改善声速和其他微分性质的描述

体积偏移通常应用于状态立方方程（EoS），以改善对密度的描述，因为它们不影响相平衡。该概念原则上可以扩展到任何其他EoS，但是基于扰动理论的EoS很少使用这种方法进行研究，这主要是因为这些方程中的大多数已经提供了准确的液体密度结果。但是，与三次方EoS一样，大多数统计缔合流体理论（SAFT）类型的EoS都难以描述派生属性，尤其是声速。在这项工作中，我们研究了扰动链统计缔合流体理论（PC-SAFT）中体积偏移的使用。提出了一种新的参数化程序，该程序涉及使用蒸气压，即从等温可压缩性获得的相对于密度的压力导数，和摩尔体积数据。最后一个属性仅适用于适应恒定的Péneloux类型的音量偏移。结果表明，该方法可以很好地描述饱和压力和液体密度，并可以更好地描述声速。通过将这种方法的结果与通过可用PC-SAFT参数集获得的结果进行比较，可以进一步研究这些变化对PC-SAFT性能和相平衡描述的影响。