We have investigated the atomic geometry of Fe films on a Ni(001) crystal i
n the thickness range 0-25 ML with the aim of following the transition from
the fee pseudomorphic structure to the equilibrium bcc phase. The structur
al techniques used are primary-beam diffraction modulated electron emission
(PDMEE) and low-energy electron diffraction (LEED). For film thicknesses u
p to 5 ML the films are fee, strained in the direction of film growth. For
higher Fe coverages, the films begin a transition to the bulk bcc structure
which is complete after 14 ML of Fe coverage. We have obtained evidence fo
r intermixing between Fe and Ni in the first 3 ML. The orientational relati
onship between the bcc phase and the underlying fee substrate has also been
investigated, finding a bcc (110) phase with four possible domains, each w
ith one of the [111] directions parallel to an fcc [110] direction. (C) 199
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