Shear instability of gamma-Fe in bulk and in ultrathin films.
Using ab initio local-spin-density calculations we demonstrate that along the Bain path describing the transformation of face-centered-cubic (fcc) gamma-Fe into body-centered-cubic (bcc) alpha-Fe, tetragonal Fe is unstable against monoclinic shear deformations producing a nearly bcc structure. In the limit of a monolayer adsorbed on a fcc substrate, the epitaxial constraint suppresses the shear instability, but in ultrathin films with three to six monolayers a striped pattern of near-bcc domains develops, confirming recent observations by scanning tunneling microscopy. A strong correlation between the shear instability and the magnetic state is reported.
Spisák
D
D
Institut für Materialphysik and Center for Computational Materials Science, Universität Wien, Sensengasse 8/12, A-1090 Wien, Austria.
Hafner
J
J