Nanopatterns of an Ultrathin Alumina Film on the Ni3Al(111)surface: a computational study
|Scientific Discipline||Materials Science|
|Principal Investigator(s)||Alessandro Fortunelli|
The aim of the Ni3Al3O3 project is to elucidate the surface structure of an ultrathin alumina film grown on the (111) surface of the Ni3Al alloy [Al2O3/Ni3Al(111)]. This film is of great scientific and technological interest because it has been shown experimentally that its surface exhibits patterns of reconstruction with an hexagonal superstructure characterized by a very large (4.14 nm) lattice parameter. Moreover, it has also been shown that these patterns are ordered in a very regular and homogeneous way over mesoscopic distances.
This system thus represents a naturally nanostructured surface which can be used as an ideal template for the growth of inorganic, bio-organic, and soft matter. For example, it is the most promising (in some respects, unique) oxide support for the preparation of ordered supra-assemblies of equally sized (monodisperse) metal nanoclusters via metal vapor deposition. Ordered arrays of size-selected metal nanoclusters would represent a breakthrough in the development of novel heterogeneous catalysts and new electronic and optoelectronic devices. The control and orientation of the metal cluster (or any) growth requires a precise understanding and modeling of the atomistic structure of the film, whence the interest of the Ni3Al3O3 project.
Furthermore, this system can be seen as the prototype of a whole class of ionic materials grown on hexagonal metal substrates.
From a structural point of view, a minimal atomistic model for the Al2O3/Ni3Al(111) film consists of a repeated unit cell containing 1200-1300 atoms.
The huge size of the unit cell calls for its delucidation an extreme computational effort that cannot be tackled within the usual framework for the allocation of cpu resources at a regional level.
Density-Functional simulated annealing simulations will be conducted on Al2O3/Ni3Al(111) cells of increasing size and variable stoichiometry to sample the structural phase space of the system, with the aim of thoroughly clarifying the nature of its peculiar reconstruction.