DIMERIZED, BUCKLED, OR IDEAL CHAINS ON THE DIAMOND (111)2X1 SURFACE

We present fully converged ab initio density-functional calculations f or the C(111)2 x 1 surface using soft carbon pseudopotentials and plan e waves with a cutoff of 42 Ry. By means of a Car-Parrinello-like ener gy-minimization scheme pi-bonded Pandey chains are found to form the g round state of the system. The surface-structural properties are studi ed in detail. Depending on the numerical details the pi-bonded chains show a nearly vanishing dimerization and are unbuckled within the accu racy of our method. Consequences for the electronic structure are disc ussed.