Bonding and reconstruction of the W(001) surface

Abstract
Ab initio calculations of the energetics of several distortions of the ideal W(001) surface are reported. We find that this surface is highly unstable against distortions which reduce the surface-atom spacings. Based on the systematics of the calculated total energy and an analysis of the electronic structure, we propose that the instability of the ideal surface can be understood in terms of a local model in which the unreconstructed surface is unstable against distortions which increase the effective coordination numbers of the surface atoms. Our results are consistent with a locally liquidlike disordered high-T phase.