QUASI-PARTICLE BANDS FOR C(111) 2X1 SURFACES SUPPORT FOR THE DIMERIZED PI-BONDED CHAIN MODEL

The GW approximation for the exchange-correlation self-energy operator is used together with a reasonable model for the surface screening fu nction to calculate quasi-particle corrections for the C(111) 2 x 1 su rface bands for several atomic configurations of the surface atoms wit hin the pi-bonded chain model. Ideal, strongly buckled, and dimerized chains are investigated. For the quasi-particle surface bands of the d imerized chain structure we find the best agreement with spectroscopic data, including the correct surface gap. Contrary to the dimerization , a buckling of the atoms in the chain does not open the gap. This res ult gives strong support for the dimerized chain structure.