Interfacial and strain energy analysis from ab initio based hierarchical multi-scale modelling: the Al–Mg–Si alloy β'' phase

Precipitate-host lattice interface studies have not traditionally been viewed as requiring
hybrid model schemes for accurate determination of the interfacial and strain energies. On the other
hand, the interfaces of main hardening precipitates of age hardenable alloys are often characterized
by both high levels of coherency and considerable subsystem misfits. Near the interface, linear
elasticity theory evidently fails in such cases to fully correctly predict the subsystem strains. Further,
density functional theory based studies on isolated supercells may prove inadequate in capturing
strain influences on the chemical interactions underlying the interfacial energy. Recent work within
the group has focussed on the implementation of a first principles based hierarchical multi-scale
model scheme, capable of determining the interfacial and strain energies for the same model system.
Choosing the fully coherent Al–Mg–Si alloy main hardening phase β'' as our test system and
limiting our studies to 2D, we discuss the variation in these energies with changing precipitate
cross-section morphology and size.