The interaction of the strong electron-acceptor tetracyanoethylene (TCNE) with the Cu(100) surface has been studied with scanning tunneling microscopy experiments and first-principles density functional theory calculations. We compare two different a
dsorption models with the experimental results and show that the molecular self-assembly is caused by a strong structural modification of the Cu(100) surface rather than the formation of a coordination network by diffusing Cu adatoms. Surface atoms become highly buckled and the chemisorption of TCNE is accompanied by a partial charge-transfer.
