INVESTIGATING BRIDGE-LIKE STRUCTURES IN A SQUARE-WELL BINARY MIXTURE USING NVT MONTE CARLO SIMULATION

Abstract

Bridge-like structures have been reported in recent studies for a binary mixture with square well fluids in 2D and 3D using different techniques. In this paper, we present our NVT simulation results in 3D with symmetric additive water and oil-like molecules. We use Dirac's delta function defined using theta step function for evaluating pressure components and surface tension values. Our investigation reveals that though 3D NVT MC results are in qualitative agreement with the published results showing all the structures as bridge-like, complete wetting of the walls by the preferred component and micelle structures but the critical parameters as surface attraction strength significantly alter to lower values for PW and CW cases in comparison to the 2D MD cases. We have studied cases with pore width as H = 6.0, 8.0, and 10.0 at T = 0.70, 0.80, and 0.90 for εAB = 0.0, 0.25, 0.50, and 1.0. For all of the bridge cases ε Wall -A = -0.50 and λ wall -A = 1.0. For fluid–fluid interaction λ ff = 1.2 and 1.5 are taken with εAA = εBB = -1.0. Our pressure and surface tension values show clear signature of confinement effect and dependence on other parameters for the bridge cases but it is concluded that different structural transitions depend only on the predefined energetically favorable and unfavorable interfaces which in turn comes from the separation of the two walls and average initial density. Our density profiles confirm the evolved structures.