Orientational Ordering on a Corrugated Substrate: Novel Pinwheel Structure forN2Adsorbed on Cu(110)

Abstract

The structure and orientational ordering of ${\mathrm{N}}_{2}$ molecules adsorbed on the Cu(110) surface is investigated in a combined experimental and theoretical study. Using He atom diffraction we find that monolayer ${\mathrm{N}}_{2}$ forms a high-order commensurate phase with an oblique unit cell. Minimum energy calculations based on realistic potentials show that the unit cell contains seven ${\mathrm{N}}_{2}$ molecules arranged in a novel type of pinwheel structure unexpected for linear molecules adsorbed on a smooth surface. Molecular dynamics simulations corroborate this structure and its remarkable thermal stability.