Density Functional Theory of Square-well Chain Mixtures Near Solid Surface

Abstract

A density functional theory is developed for square-well chain mixtures near a hard wall or a square-well wall. The Helmholtz free energy functional is divided into two parts, an ideal-gas contribution and an excess contribution. The later is constructed based on weighting density approximation and coarse graining approximation. For simplicity, a Heaviside function is used as the weighting function. To calculate the density profiles of beads, a direct iterative algorithm combined with a relaxation factor is used. A single chain simulation in an effective field is needed in each iterative step. The theoretical results are in good agreement with Monte Carlo simulation.

Keywords:

• Density functional theory
• Square-well chain mixture
• Reference interaction site model
• Helmholtz energy

Acknowledgements

This work was supported by National Science Foundation of China (Project No. 20025618, 20236010), the Doctoral Research Foundation by Ministry of Education of China (Project No.1999025103) and the Education Committee of Shanghai City of China.