Surface relaxation and ferromagnetism of Rh(001)

The significant discrepancy between first-principles calculations and experimental analyses for the relaxation of the (001) surface of rhodium has been a puzzle for some years. In this Letter we present density-functional theory calculations using the local-density approximation and the generalized gradient approximation of the exchange-correlation functional. We investigate the thermal expansion ii of the surface and the possibility of surface magnetism. The results throw light on several, hitherto overlooked, aspects of metal surfaces; We find that when the free energy is considered density-functional theory provides results in good agreement with experiments.