Properties of the liquid-vapor interface of square-well fluids with ranges of interaction lambda=1.5, 2.0, and 3.0 are obtained by Monte Carlo simulations and from square-gradient theories that combine the Carnahan-Starling equation of state for hard spheres with the second and third virial coefficients. The predicted surface tensions show good agreement with the simulation results for lambda=2 and for lambda=3 in a temperature range reasonably close to the critical point, 0.8=T/T(c)=0.95. As expected, the surface tension increases with the range of interaction and decreases monotonically with temperature. A comparison between theory and simulation results is also given for the width of the interface and for the coexistence curves for the different interaction ranges.
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http://dx.doi.org/10.1063/1.1740749 | DOI Listing |
J Chem Phys
January 2025
Department of Chemistry, Chicago Center for Theoretical Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA.
Bottom-up coarse-grained (CG) modeling is an effective means of bypassing the limited spatiotemporal scales of conventional atomistic molecular dynamics while retaining essential information from the atomistic model. A central challenge in CG modeling is the trade-off between accuracy and efficiency, as the inclusion of often pivotal many-body interaction terms in the CG force-field renders simulation markedly slower than simple pairwise models. The Ultra Coarse-Graining (UCG) method incorporates many-body terms through discrete internal state variables that modulate the CG force-field according to, e.
View Article and Find Full Text PDFJ Colloid Interface Sci
December 2024
Department of Mechanical Engineering (Robotics), Guangdong Technion - Israel Institute of Technology, Shantou, Guangdong 515063, China.
Hypothesis: Current models for receding contact angles of Cassie-Baxter state droplets on textured hydrophobic substrates are applicable only to a specific structural type, e.g., pillar (above which a droplet has isolated contact line and continuous liquid-vapor interface) or pore (continuous contact line and isolated liquid-vapor interface), signifying a lack of universality.
View Article and Find Full Text PDFJ Chem Phys
November 2024
Department of Mechanical Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
Through the decomposition of the pressure into the kinetic and the intermolecular contributions, we show that the pressure anisotropy in the fluid interface, which is the source of the interfacial tension, comes solely from the latter contribution. The pressure anisotropy due to the intermolecular force between the fluid particles in the same or the different fluid components is approximately proportional to the multiplication of the corresponding fluid density gradients, and from the molecular dynamics simulation of the liquid-vapor and liquid-liquid interfaces, we demonstrate that the density gradient theory by van der Waals gives the leading order approximation of the free energy density in inhomogeneous systems, neglecting the Tolman length.
View Article and Find Full Text PDFJ Chem Phys
November 2024
Maxwell Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
The calculation of the interfacial free energy between two thermodynamic phases is crucial across various fields, including materials science, chemistry, and condensed matter physics. In this study, we apply an existing thermodynamic approach, the Gibbs-Cahn integration method, to determine the interfacial free energy under different coexistence conditions, relying on data from a single-state calculation at specified pressure and temperature. This approach developed by Laird et al.
View Article and Find Full Text PDFJ Phys Chem Lett
November 2024
Department of Mechanical Engineering (Robotics), Guangdong Technion - Israel Institute of Technology, Shantou, Guangdong 515063, China.
It is common sense that the droplet is stickier to substrates with larger solid-liquid contact areas. Here, we report that this intuitive trend reverses for hollowed micropillars, where a decrease in solid-liquid contact area caused by an increase in the pore size of a pillar top leads to an increase in the droplet depinning force. As compared to relief of liquid-vapor interface distortion caused by the sliding of the contact line on filled pillars, the pore hinders the contact line sliding, hence leading to enhanced interface distortion and droplet adhesion.
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