Stability and structure of atomic chains on Si(111)

We study the stability and structure of self-assembled atomic chains on Si(111) induced by monovalent, divalent and trivalent adsorbates, using first-principles total-energy calculations and scanning tunneling microscopy. We find that only structures containing exclusively silicon honeycomb or silicon Seiwatz chains are thermodynamically stable, while mixed configurations, with both honeycomb and Seiwatz chains, may be kinetically stable. The stability and structure of these atomic chains can be understood using a surprisingly simple electron-counting rule.