Investigation of Surface Tensions for Pure Fluids outside and inside the Critical Region

Abstract

An equation of state (EOS) applicable for both the uniform and non-uniform fluids was established by using the density-gradient expansion, in which the influence parameter κ[ρ(r),T] was obtained by the use of direct correlation function. The density functional theory (DFT) provides a framework under which both the phase equilibria and interfacial properties can be investigated within a single set of molecular parameters. The phase equilibria inside the critical region can be improved by the renormalization group theory (RGT). However, the correction of interfacial properties by DFT and RGT is computationally difficult. In the present work, the density gradient theory (DGT) in which κ[ρ(r),T] is treated as a constant is used to combine with the RGT for interfacial properties inside the critical region.

Study on Vapor‐Liquid Nucleation Rates for n‐Alcohols by Density Functional Theory

“…DFT is theoretically better than DGT because in the calculations of interfacial properties and nucleation properties, DFT only needs the molecular parameters regressed from bulk properties as input. However, in the calculation of DGT, for the determination of both surface tension [53][54][55] and nucleation rates, 42 additional influence parameters are need. Figure 3 shows the predicted nucleation rates of ethanol and the comparisons with experimental data.…”

Phase Equilibria and Plate‐fluid Interfacial Tensions for Four‐site Associating Lennard‐Jones Fluids Confined in Slit Pores

“…The Helmholtz free energy functional due to the hard sphere repulsion is represented by MFMT, which conjectures that the excess intrinsic Helmholtz energy functional can be expressed in the form of: 19,[53][54][55][56][57][58][59] ( ) 1 2 V1 V2 hs 0 3 3 3 2 2 2 2 V 2 3 3 3 2 3 3 3 [ ( )] kT ln(1 ) 1…”

Investigation of Vapor‐Liquid Nucleation for Associating Fluids by Density Gradient Theory

“…Besides DFT, another theoretical approach, density gradient theory (DGT), [29][30][31][32][33][34][35][36][37][38] is also applicable to vapor-to-liquid nucleation. In the calculation of the surface tension and nucleation properties, the main difference between these two theories is that DFT only needs the molecular parameters as input, while DGT needs an additional influence parameter κ that should be obtained by fitting to the experimental data.…”

“…In the calculation of the surface tension and nucleation properties, the main difference between these two theories is that DFT only needs the molecular parameters as input, while DGT needs an additional influence parameter κ that should be obtained by fitting to the experimental data. [35][36][37][38] In general, DFT is theoretically better than DGT but DGT is able to provide more accurate predictions by adjusting the influence parameter. Recent studies [35][36][37][38] on surface tensions show that DGT preserves all the advantages of DFT in capturing the structure and properties of vapor-liquid surface but gives much more accurate surface tensions.…”

“…[35][36][37][38] In general, DFT is theoretically better than DGT but DGT is able to provide more accurate predictions by adjusting the influence parameter. Recent studies [35][36][37][38] on surface tensions show that DGT preserves all the advantages of DFT in capturing the structure and properties of vapor-liquid surface but gives much more accurate surface tensions.…”