  Strain and strain adaption mechanisms in modern functional materials are of
crucial importance for their performance. Understanding these mechanisms will
advance innovative approaches for material properties engineering. Here we
study the strain adaption mechanism in a thin film model system as function of
epitaxial strain. Chemically disordered FeRh thin films are deposited on W-V
buffer layers, which allow for large variation of the preset lattice constants,
e.g. epitaxial boundary condition. It is shown by means of high resolution
X-ray reciprocal space maps and transmission electron microscopy that the
system reacts with a tilting mechanism of the structural units in order to
adapt to the lattice constants of the buffer layer. This response explained by
density functional theory calculations, which evidence an energetic minimum for
structures with a distortion of c/a =0.87. The experimentally observed tilting
mechanism is induced by this energy gain and allows the system to remain in the
most favorable structure. In general, it is shown that the use of epitaxial
model heterostructures consisting of alloy buffer layers of fully miscible
elements and the functional material of interest allows to study strain
adaption behaviors in great detail. This approach makes even small secondary
effects observable, such as the directional tilting of the structural domains
identified in the present case study.
