DENSITY PROFILE OF LIQUID-METAL SURFACE WITHIN THE SQUARE-GRADIENT APPROXIMATION - DENSITY-FUNCTIONAL APPROACH

The density profile of a liquid metal surface is calculated from densi ty-functional theory within the square-gradient approximation. The asy mptotic solutions of the Euler-Lagrange equations, which determine ion and electron surface density profiles, are obtained analytically in t he bulk liquid phase. Using these solutions as the trial functions for the variational calculation, the ion and electron density profiles of liquid alkali metals are determined simultaneously. Both ion and elec tron density profiles show oscillations similar to those predicted fro m reflectivity measurements and computer simulations.