Core-level energy shifts for the beryllium surface region are calculated by means of a Green’s function technique within the tight-binding linear muffin-tin orbitals method. Both initial- and final-state effects in the core-ionization process are fully accounted for. Anomalously large energy shifts are found for the three topmost surface layers in agreement with recent experimental data. The reason for this extraordinary behavior is explained.
Physical Review Letters, 1993, Vol 71, Issue 15, p. 2457-2460