Density functional study of pressure profile for hard-sphere fluids confined in a nano-cavity

Zongli Sun,Junxia Zhang,Yanshuang Kang

doi:10.1063/1.4867011

Zongli Sun, Junxia Zhang + Show 1 more

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https://doi.org/10.1063/1.4867011

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Abstract

To gain a deeper understanding and to master the mechanical properties of classical fluids confined in nano-geometry, the pressure tensor applicable to confined fluids is derived by taking into account more correlation among the particles. First, based on classical statistical theory, the expression for the pressure tensor is calculated by expanding the stress tensor and considering further the correlation effect among the particles. Our numerical result is compared with that of molecular dynamics simulation and the agreement between them is quite good. Then, the dependence of the bulk density and the dimension of the cavity on the pressure profile is computed and studied. The curvature dependence of contact pressure and net pressure on the cavity wall is also studied. Finally, the solid–fluid interfacial tension is calculated and compared with Monte Carlo results. The results derived in this work indicate the importance and necessity of correlation among particles in the prediction of the mechanical properties of confined fluids.

Highlights

Pressure tensor in fluids is an important mechanical quality, which relates closely to capillarity, interfacial phenomena and hydrodynamics, but provides useful information about mechanical deformation, heat transform and phase transition.[1,2,3] As is well known, the pressure p for a homogeneous fluid is isotropic, and is defined as one-third of the trace of the pressure tensor
To gain a deeper understanding and to master the mechanical properties of classical fluids confined in nano-geometry, the pressure tensor applicable to confined fluids is derived by taking into account more correlation among the particles
The results show that when the curvature is large, the net pressure increase is extreme with the curvature, while it increases slowly when the curvature is small

Summary

Introduction

Pressure tensor in fluids is an important mechanical quality, which relates closely to capillarity, interfacial phenomena and hydrodynamics, but provides useful information about mechanical deformation, heat transform and phase transition.[1,2,3] As is well known, the pressure p for a homogeneous fluid is isotropic, and is defined as one-third of the trace of the pressure tensor. Several treatments have been proposed for the calculation of the local pressure from the intermolecular forces In the main, these proposals have focused on the definition of the integration contour connecting the positions of two interacting particles. The Irving-Kirkwood contour[6] defines a straight line between particles, while the Harasima contour[7] depends on the symmetry of the system under consideration. The latter has been found to give unphysical results when it is employed in the spherical coordinate system.[8] the Irving-Kirkwood contour has been popularly used in both theoretical investigation and computer simulations. Some researchers have reported results which have taken into account the

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