1. Friction Laws for Dry Nanoscale Contacts Izabela Szlufarska (University of Wisconsin - Madison) DMR 0512228 How does friction force depend on applied load and contact area? Macroscopic contacts: (Amontons’ law 1699), Nanoscale contacts: Laws Unknown Approaches: AFM experiments for contacts nm-µm in size. Interpreted through continuum mechanics models: Continuum mechanics breaks down in nanoscale contacts. This study: PI performed molecular dynamics simulations of AFM experiments at realistic length scales. Highly accurate REBO potentials are used to simulate mechanical deformation and chemical reactions of diamond simultaneously. Models give very good agreement with experiments on H-terminated diamond interfaces. Friction coefficient ~0.05 (exp: ~0.02), shear strength ~1,000 MPA (exp: 200 - 1,000 MPa). Discovery: AFM tip is not smooth. It consists of multiple atomic size asperities (total area A real ). Friction force is always proportional to this area: Atomic roughness and interfacial interactions govern friction behavior Non-adhesive nanoscale contacts follow macroscopic laws of friction: Adhesive contacts are well described by continuum models: Atomic multi-asperity model is proposed to describe simulation results. Transition from linear to non-linear friction due to increased adhesion Non- adhesive contact Adhesive contact

2. Education in Computational Materials Science Izabela Szlufarska (University of Wisconsin) DMR 0512228 Undergraduate mentoring: Paul Kamenski (Materials Science & Engineering) Supported by PI’s lab for 2 years Wrote codes to support molecular dynamics simulations of nanocrystalline materials Co-op at the Oak Ridge National Laboratory through PI’s collaborations In the Spring ‘08 won NSF Graduate Research Fellowship (GRFP) In the Fall ‘08 begins graduate studies in materials science at Oxford University Interdisciplinary course: Molecular Dynamics and Monte Carlo Simulations in Materials Science Taken by students across different colleges and departments (materials science & engineering, mechanical engineering, chemical engineering, chemistry, nuclear engineering, engineering mechanics, geophysics). Most students come from experimental groups Students work on interdisciplinary teams and on individual projects Final project examples: “Reverse Monte Carlo for Amorphous Si” “Radiation damage in nanoparticles” “Investigation of solid-water interface using LAMMPS” “Polymer bulk erosion: Monte Carlo simulations” “Modeling of phonon density of states for a Si/Ge heterostructures” Graduate student Sarah Khalil presents her final class project Undergraduate student Paul Kamenski

3. Ferrite (α) BCC a = 2.870 Å Austenite (γ) FCC a = 3.515 Å 910 °C Education in Computational Materials Science Izabela Szlufarska (University of Wisconsin) DMR 0512228 Example of student’s work from the course: MD and MC Simulations in Materials Science Andy Nelson (graduate student in experimental group in Nuclear Engineering): “Modeling of Ferrite-Austenite Transition” ASM Materials Handbook Vol. 9