טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentFeruz Yosi
SubjectThe Strength of Nanoparticles with Face-Centered Cubic (FCC)
Lattice Structure under Compression in Molecular
Dynamics Simulation
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Dan Mordehai
Full Thesis textFull thesis text - English Version


Abstract

Understanding dislocation nucleation is key to control plasticity of defect-free specimens. Here, we perform an atomistic study of the strength of various FCC defect-free nanoparticles. Simulations of compression are performed on Wulff shaped nanoparticles of various FCC metals along the [111] crystallographic direction. For some metals more than one interatomic potential were used. We show here that all nanoparticles yield by nucleating Shockley partial dislocations at the vertices. The aim of this research is to investigate the strength of those particles depending on their size, in order to examine a universal law for the stresses required to create dislocation on the vertices of those particles. The compressive stress at which the partial dislocations nucleate is smaller for larger particles for all FCC metals. The dependence of the strength on the size obeys a power-law, with a universal exponent for all FCC nanoparticles. The pre-factor of the power-law relationship depends on material properties. Based on dimensional analysis and classical nucleation theory of dislocations, we propose that the exponent corresponds to the geometry, which is similar to all FCC metals, and the pre-factor is linearly increasing with a dimensionless parameter, which holds within it different material properties. Based on these results, we discuss a universal law for the strength of FCC nanoparticles and its fundamental difference from the universal law found experimentally for FCC pillars.