EFFECT OF SUBSTRATE-IMPOSED STRAIN ON THE GROWTH OF METALLIC OVERLAYERS CALCULATED FOR FCC AND HCP IRON

By means of electronic-structure calculations with use of the full-potential linear-muffin-tin-orbital method and the local spin-density approximation (LSDA), the influence of the substrate-imposed strain on a fcc (111) or hcp (000 1) iron layer is determined. A careful treatment of the elastic effects predicts that the nonmagnetic hcp structure is more stable than the nonmagnetic fcc structure for a wide range of lattice constants but becomes less favorable for a large positive or negative strain on the overlayers. The stabilization of the fcc structure at large mismatches is traced to the stiffer hcp interplanar bonds, a consequence of the decreased axial c/a ratio. It is argued that similar behavior should be found for the other transition metals. The results are prototypical for the substrate-overlayer elastic interaction but cannot be compared directly to experiment because of systematic LSDA errors in the magnetic-ferromagnetic energy difference for iron.