It was noted that S-decorated Cu trimers were a likely agent for S-enhanced Cu transport between islands on Cu(111). According to ab initio calculations, an excellent bonding of S to trimer-Cu dangling valences resulted in an ad-Cu3S3 formation energy of only 0.28eV; compared to the 0.79eV for a self-adsorbed Cu atom, and a diffusion barrier of 0.35eV.

Formation and Diffusion of S-Decorated Cu Clusters on Cu(111). P.J.Feibelman: Physical Review Letters, 2000, 85[3], 606-9