偶极-四极相互作用的汽液平衡模拟和状态方程贡献
Vapor-liquid equilibria simulation and an equation of state contribution for dipole-quadrupole interactions
摘要：
采用分子模拟方法对偶极和四极流体的汽液平衡进行了系统的研究，提出了一种新的状态方程的亥姆霍兹能量贡献。本文研究了12种双中心Lennard-Jones加点偶极和点四极模型流体（2CLJDQ）在不同约化偶极矩μ ^{*2}= 6，12，约化四极矩Q^{*2}= 2，4和约化伸长L^*=0，0.505，1的情况。温度覆盖从每种流体的临界温度的约55%至约95%的宽范围。用NpT +试验粒子方法计算了非球形分子的饱和蒸气压、饱和密度和饱和饱和比，拟合得到了临界数据和偏心因子，并在此基础上建立了非球形分子偶极-四极交叉相互作用的状态方程.该表达式是基于三阶微扰理论和模型常数进行调整，目前的2CLJDQ模拟结果。当应用到混合物，该模型被发现是在很好的协议，从模拟和实验结果。新的EOS贡献也与基于段的EOS兼容，如各种形式的统计缔合流体理论（SAFT）EOS。
英文摘要：
A systematic investigation on vapor-liquid equilibria (VLE) of dipolar and quadrupolar fluids is carried out by molecular simulation to develop a new Helmholtz energy contribution for equations of state (EOS). Twelve two-center Lennard-Jones plus point dipole and point quadrupole model fluids (2CLJDQ) are studied for different reduced dipolar moments mu^{*2}=6,12, reduced quadrupolar moments Q^{*2}=2,4 and reduced elongations L^*=0, 0.505,1. Temperatures cover a wide range from about 55% to about 95% of the critical temperature of each fluid. The NpT + test particle method is used for the calculation of vapor pressure, saturated densities and saturated enthalpies.Critical data and the acentric factor are obtained from fits to the simulation data.On the basis of this data, an EOS contribution for the dipole-quadrupole cross-interactions of non-spherical molecules is developed. The expression is based on a third-order perturbation theory and the model constants are adjusted to the present 2CLJDQ simulation results. When applied to mixtures, the model is found to be in excellent agreement to results from simulation and experiment. The new EOS contribution is also compatible with segment-based EOS, like the various forms of the Statistical Associating Fluid Theory (SAFT) EOS.
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