1. Length-scale Dependent Dislocation Nucleation during Nanoindentation on Nanosized Gold Islands Alex Gonzalez Department of Mechanical Engineering University of Arkansas Fayetteville, AR 72701 USA REU 2 nd Week Seminar – Friday May 29 th, 2009

2. Multiscale Mechanics of Materials Laboratory, Department of Mechanical Engineering Literature Background Molecular Dynamics  Requires 3 things:  Interatomic potential energy function, which defines the interactions between atoms  Forces between atoms, which are derived from the binding energies  A numerical method to compute the velocities and positions of atoms in the simulation http://www.fisica.uniud.it/~ercolessi/md/

3. Multiscale Mechanics of Materials Laboratory, Department of Mechanical Engineering Literature Background

4. Multiscale Mechanics of Materials Laboratory, Department of Mechanical Engineering Methodology and Goals The objective of this project is to make indentations on nanosized islands of Au to generate dislocations and study the onset of plasticity. Computer Simulation  Linux  Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS)  Ensight  Super Computer “Trillion” Week 1-3: Visualization Week 4-5: Initial Testing Week 6-8: Analysis & additional Simulations Week 9-10: Report and Presentation Norbert Attig, Kurt Binder, Helmut Grubm¨ uller, Kurt Kremer (Eds.), John von Neumann Institute for Computing, J ¨ ulich, NIC Series, Vol. 23, ISBN 3-00-012641-4, pp. 1-28, 2004.

5. Multiscale Mechanics of Materials Laboratory, Department of Mechanical Engineering Overview 3D Rendering Input corresponding MD material specifications. Input correct settings for server and files. Simulation Run simulation of LAMMPS through “Trillion.” Export data from LAMMPS Simulation. LAMMPS Import data from LAMMPS. Set visualization preferences i.e. dots, spheres, energy, Centro-symmetry. Interpret 3D model results. Step1 Step2 Step3

6. Multiscale Mechanics of Materials Laboratory, Department of Mechanical Engineering Nanosized Islands

7. Multiscale Mechanics of Materials Laboratory, Department of Mechanical Engineering Nanoindentation Nanoindentation – to probe and analyze the properties of a specimen at nanoscale resolution  500 nm  5.5 μN  (150 nm)  11 μN (300 nm)

8. Multiscale Mechanics of Materials Laboratory, Department of Mechanical Engineering Nanosized Islands P5 P4 P6 P1 P3 P2

9. Multiscale Mechanics of Materials Laboratory, Department of Mechanical Engineering EnSight simulated Nanoindentation