Nanostructure (Structure of Nanograins)
Nanostructure Model
Schematic, tentative model of a nanograin. The atoms in the surface shell are compressed relative to the relaxed lattice.
- Ro - radius of the core
- so - thickness of the surface layer (shell)
- ao - lattice parameter in the core
- as - lattice parameter in the shell.
ZnS MD Model
Model of a 4 nm in diameter grain of ZnS obtained by Molecular Dynamics (MD) simulations. The above MD model confirms that the arrangement of atoms at the surface of the grain differs from the mostly regular arrangement in the grain core.
Zn-S Stress
Distribution of strains along the radius in ZnS grain constructed with MD simulation technique. The graph above shows, that in the central part of the grain the lattice is relaxed, but becomes increasingly compressed towards the grain surface. This effect is stronger in smaller size grain. Shortening or elongation of the interatomic bonds found experimentally can be interpreted as a result of compressive stress or tensile stress, respectively.
Diamond Grain
Model of a nanocrystalline diamond grain. The model to the right shows somewhat more complex structure than that shown earlier. In addition to the core and surface shell, the grain is surrounded by a layer of graphite ‘flakes’.