K.P. Zolnikov

Local structural transformations in the fcc lattice in various contact interaction. Molecular dynamics study

The work is a molecular dynamics study of the peculiarities of local structural transformations in a copper crystallite at the atomic level in contact interaction of various types: shear loading of perfectly conjugate surfaces, local shear loading and nanoindentation. Interatomic interaction is described in the framework of the embedded atom method. It is shown that initial accommodation of the loaded crystallite proceeds through local structural transformations giving rise to higher-rank defects such as dislocations, stacking faults, interfaces, etc. In further plastic deformation, the structural defects propagate from the contact zone to the crystallite bulk. The egress of structural defects to a free surface causes deformation of the model crystallite. The deformation pattern can evolve, depending on the loading conditions, with a change in crystallographic orientation of the crystallite near the contact zone, generation of misoriented nano-sized regions, and eventually formation of a stable nanostructural state. The obtained results allow conceptually new understanding of the nature of defect generation in a crystalline structure during the nucleation and development of plastic deformation in loaded materials.

Protodefect as a Basis of Multilevel Nanoscale Plasticity of Crystal Materials

Atomic mechanisms of plastic deformation initiation in materials with crystal structure are investigated. It is shown that thermal fluctuations can be a reason for structural defect generation and there is a threshold strain value at which zones with local structural changes (protodefects) grow almost abruptly. The calculations illustrate that protodefect formation is induced by a local expansion of atomic volume.

Molecular Dynamic Study of Proto-Faults Generation as an Atomistic Mechanism of Incipient Plasticity during High-Speed Loading in Ideal Crystal

The molecular dynamics investigation of plastic deformation initiation has shown that at the first stage local structural distortions, i.e. protodefects that give rise to conventional lattice defects, are generated. We study in detail the dynamics of atomic displacements that govern protodefect nucleation. The calculations illustrate that protodefect formation is induced by a local expansion of atomic volume. The stage-by-stage generation of protodefects in the conditions of relaxation unambiguously correlates with potential energy variation in the crystallite.