Attractive interaction between alkali-metal adatoms on metal surfaces.

Abstract

An effective interaction ${\mathit{V}}_{\mathrm{ad}}$ between adatoms which are randomly chemisorbed on a metal surface is calculated. ${\mathit{V}}_{\mathrm{ad}}$ is composed of a repulsive dipole interaction and an attractive cohesive interaction. ${\mathit{V}}_{\mathrm{ad}}$ is self-consistently determined in a linear combination of atomic orbitals model with nonorthogonal orbitals by using a cell coherent-potential approximation theory. It follows that while the dipole interaction is dominant in the low-coverage region, it decreases with increasing coverage and is surpassed by the cohesive interaction at high coverage; that is, ${\mathit{V}}_{\mathrm{ad}}$ becomes attractive. This result is consistent with the experimental result of low-energy electron diffraction and electron-energy-loss spectroscopy on K/Cu(100).