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Molecular Dynamics Simulation of the Mechanical Properties of Au Nanowires under Tensile Strain

Author: FengWenJuan
Tutor: ChenYing
School: Shandong Institute of Architecture
Course: Condensed Matter Physics
Keywords: molecular dynamics simulation nanowire mechanical property yielding strength elastic modulus
CLC: TB383.1
Type: Master's thesis
Year: 2011
Downloads: 148
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Abstract


Nanomaterials have extraordinary mechanical, electrical, thermal and magnetic properties. With the fast development of nano science and technology especially with the development of microelectronic devices more and more attention is paid to metal nanowires which are important parts of nanomaterials. Metal nanowires are important components of nanoscale devices. Investigation on the mechanical properties is one of the key challenges that need to be overcome for the future technological applications of nanomaterials and will play an important role on the reliability and stability of microelectronic devices.Molecular dynamics simulation is used widely which is one kind of computer simulations. Molecular dynamics simulation is employed in this paper. This paper focuses on the molecular dynamics simulation of the mechanical properties of Au nanowires with various cross-sections, with various strain rates and with various temperatures, emphasizing on the analysis of the elastic modulus and yielding strength. The embedded-atom-method potential is employed to represent the atomic interactions. Verlet algorithm is used to integrate Newton’s equations of motion.There are two stages during the extension of an Au nanowire, elastic stage and plastic stage. Stress-strain curve can be obtained by obtaining the stress and the strain in every moment. The elastic modulus can be obtained by derivation calculus of stress to strain in the elastic stage of stress-strain curve. And the peak stress is defined as yielding strength.Simulations of seven Au nanowires under tensile loading at various section cross sizes at the same temperature subjected to the same strain rate show the effects of section cross sizes to the mechanical properties of Au nanowires under tensile loading. This paper presents that there are two different stages consistent with the stress-strain curve by analyzing the stress-strain curve, the yielding strength and the elastic modulus. The linear phase of stress-strain curve is consistent with the elastic stage and the nonlinear phase of stress-stain curve after the breakdown point is consistent with the plastic stage. There are stacking faults emerging substantially in plastic stage. The stress of nanowire decreases dramatically after the breakdown point fluctuating within limits. The nanowires with smaller cross-sections yield earlier with strain more. This phenomenon is associated primarily with the high surface-to-volume ratio at the nanoscale level. The elastic modulus decreases with decreasing size of cross-section, while yielding stress increases with decreasing size of cross-section for the same length of Au nanowires.Simulations of Au nanowires under tensile loading subjected to various strain rates at the same temperature with the same cross-section show that the nanowire with the higher strain rate yields earlier and easier with the strain more. The elastic modulus increases with increasing strain rate while inapparent and the second yielding occurs easier. Simulations of Au nanowires under tensile loading at various temperatures subjected to the same strain rate with the same cross-section show that the elastic modulus and the yielding strength of Au nanowire decrease approximately linearly with increasing temperature.

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