Structure of H-covered Be(0001)

In accord with the inverse bond-order--bond-length correlation expected for group-II elements, linearized augmented-plane-wave (LAPW) calculations show that a 1×{}1 monolayer of H, adsorbed on Be(0001), should cause the outer Be layers' separation to be close to ideal, i.e., to be contracted relative to the substantial expansion seen for clean Be(0001). However, the LAPW work functions, and also the H-induced surface-state and resonance positions calculated for 1×{}1 H overlayers, are in poor agreement with experiment. Based on the known accuracy of LAPW calculations, these disagreements indicate that at monolayer coverage, adsorbed H does not all reside above the outer Be layer.