Energetics of Surface Multilayer Relaxation on W (001): Evidence for Short-Range Screening

Multilayer relaxation of the W (001) surface is explored by the all-electron local-density-functional total-energy approach. In agreement with recent experiments, we find a contraction of the topmost interlayer spacing by 5.7%. Surprisingly, the amount of this contraction is independent of the relaxation of the inner layers, which are predicted to be expanded by 2.4% and 1.2% for the second and third interlayer spacings, respectively. Thus, the driving mechanism for the relaxation process appears to be of a local nature because of short-range screening effects at the transition-metal surface.