Molecular-dynamics study of thin iron films on copper

We have studied the structural stability of thin gamma-iron films on Cu(001 ) and Cu(111) substrates using molecular-dynamics simulations in combinatio n with a semiempirical model. Experimentally, the stability of such films h as turned out to depend on (growth) temperature and film thickness. On incr easing the thickness or decreasing the temperature the films undergo a stru ctural change to the bcc structure, which is well reproduced by our simulat ions. An analysis of the local atomic environment of the films after the st ructural transformation shows that, especially on Cu(001), only parts of th e film accomplish the transformation into the bcc structure. Considerations of the atomic displacements during the transformation allow us to give an explanation of the different stability of the films on Cu(001) and Cu(111) as well as the observed orientational relationships.