A new exchange–correlation functional free of delocalization and static correlation errors

A combination of weighted density approximation and classical mapping leads to a new exchange–correlation energy free of delocalization and static correlation errors in Kohn–Sham density functional theory.

DENSITY FUNCTIONAL THEORY AND FREEZING OF HARD SPHERES, BEYOND THE PERCUS–YEVICK APPROXIMATION

The density functional theory for the freezing hard spheres is studied. We use a variety of the hard sphere direct correlation functions (DCFs) such as the one introduced by Roth et al. [J. Phys. Condens. Matter14, 12063 (2002)]; we call it RELK DCF, a new hard sphere DCF developed here by a combination of the RELK and the Percus–Yevick DCFs, and finally the generalized mean spherical approximation (GMSA). The structure factor, the freezing, and order parameters are calculated using these DCFs. The structure factor obtained by the new DCF is in good agreement with the Monte Carlo simulation. The best result for the freezing parameters in comparison with the Monte Carlo simulations is obtained by using our new expression for the DCF. Finally we obtain the Helmholtz free energy of the hard sphere FCC crystals using modified weighted density approximation (MWDA), and again the best results are obtained by using the new expression for the hard sphere DCF.

LOCAL DENSITY DISTRIBUTION OF NONUNIFORM POLYMER MELTS AT SOLID-FLUID INTERFACES

We have developed the density functional theory (DFT) and density functional perturbation theory (DFPT) which are based both on the hybrid weighted-density approximation and on the higher-order weighted-density approximation, respectively, to study the structural and thermodynamic properties of polymer melts at interfaces. They were applied to predict the local density distributions, adsorption isotherms, surface excesses, and solvation forces of a freely jointed tangent hard-sphere chain in hard slit pores. The Wertheim's first-order perturbation theory extended by Yu and Wu [J. Chem. Phys.117, 2368 (2002)] was used to calculate the excess free energy and second-order direct correlation function due to the chain connectivity. The weight functions were calculated from the second-order direct correlation functions. The calculated results show that the DFT is in excellent agreement with the computer simulations and slightly better than the DFPT.