Abstract:
We report on experimental study and theoretical analysis of pentagonal (five-fold) symmetry in micro- and nanocrystalline objects: metallic particles and elongated rods. The observations of electrodeposited small particles with decahedral and icosahedral morphology and rods with pentagonal cross-section, are presented. Internal structure of pentagonal objects is explained as a result of multiple twinning in a material with FCC crystal structure and formation of disclination defects. Knowledge on the disclination content of pentagonal objects allows one the elaboration of qualitative and quantitative models for their structural evolution and stability. To build such models, elasticity of disclination in finite size bodies is discussed in full details. Various relaxation processes leading to the diminishing of the internal energy of disclinated particles and elongated rods are proposed. These processes include the emergence of a hole at dislocation core, generation of additional dislocation defects inside pentagonal objects, and formation of the crystal lattice-mismatch layer on the particle or rod surface. The operation of the listed relaxation mechanisms is documented by available experimental data.
The content of the report is based mainly on the following publications:
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