Theory of metallic clusters: Asymptotic size dependence of electronic properties

For a spherical metallic cluster of large radius R, the total energy is E=α4π${\mathit{R}}^3$/ 3+σ4π${\mathit{R}}^2$+γ2πR, the chemical potential is μ=-W-c/R, and the first ionization energy I and electron affinity A are -μ±1/2(R+d). By solving the Euler equation within the Thomas-Fermi-Dirac-Gombas-Weizsäcker-4 approximation for jellium spheres with up to ${10}^6$ electrons, we extract the surface energy σ, curvature energy γ, work function W, and constants c and d. The constant c is not zero, but neither is it -1/8, the prediction of the image-potential argument. We trace c to the second- and fourth-order density-gradient terms in the kinetic energy, which are present even in systems with no image potential. However, the constant d is found to be the distance from a planar surface to its image plane. In the absence of shell-structure oscillations, the asymptotic forms hold accurately even for very small clusters; this fact suggests a way to extract the curvature energy of a real metal from its surface and monovacancy-formation energies. We also discuss asymptotic ${\mathit{R}}^{\mathrm{-}1}$ corrections to the electron density profile and electrostatic potential of a planar surface.