Disagreement between experimental and theoretical metal surface relaxations

A cornerstone of our understanding of surface structure is that outer-layer separations of dose-packed metal surfaces are within a percent or two of corresponding bulk interlayer spacings. Largely based on low energy electron diffraction (LEED) analyses, this conventional wisdom co-exists in the literature with numerous first-principles calculations that predict considerably larger surface contractions for reactive metals. Achieving a realistic, comprehensive understanding of bonding at surfaces requires that we uncover the source of the discrepancies.