Hello, A new project on the LCRC cluster has been requested. Please forward the information on to the LCRC Allocation sub-committee. Applicant's name: Meng Shen Applicant's institution: ANL Applicant's division: NST Project Name: Superlubricity_ND_2D Project title: Mechanisms of superlubricity emerging from nanodiamonds and 2D materials Associated funding: DOE Division of Materials for Energy Other Systems: Carbon, 100,000 SU Science: Macroscopic superlubricity was realized when graphene rolls over nanodiamond (1). Here we propose to use ab-initio and molecular dynamics (MD) simulations to investigate the mechanisms and potentials of graphene and other 2-D materials in understanding the detailed mechanism of superlubricity. By systematic comparative studies, we will investigate how the graphene/nanodiamond interfacial interactions affect the friction properties. Furthermore, we will uncover the atomic level mechanisms of superlubricity when graphene is replaced with MoS2, using ab-initio simulations in combination with MD simulations. This computational and theoretical research targets to build a roadmap for achieving superlubricity by combining nanodiamond with 2D materials. Reference(s): (1) D. Berman et al., Science 348, 1118 (2015). Project description: We intend to use ab-initio simulations and Molecular Dynamics (MD) simulations to unravel the mechanisms why the superlubricity is achieved by rolling nanodiamonds over 2D materials such as graphene and MoS2, when the 2D layers are depleted and diamond is covered by graphitic layers, while not achieved directly by graphitized nanodiamonds. We will start from comparing graphitized nanodiamonds and nanodiamonds (typically 3 nm, or ~3000 atoms) mechanically wrapped by graphene, using both Airebo and reax force fields. Both Airebo and Reax include the short range and longer range (such as inter-plane) interactions, but fitted in different philosophies. Keeping in mind that both force fields overestimate the energy barrier for diamond amorphatization by 100%, we investigate, in atomic level, whether the carbon ring structure (such as stone-wales defects), surface morphology, elastic modulus, inter-layer interactions or the contact area is the key to superlubricity. The lubricity test is accomplished by pressing and sliding a DLC (160 Å by 60 Å by 30 Å, or 55080 atoms) against a graphene sheet with a nanodiamond in between. Also we intend to understand how MoS2 facilitates phase transition of nanodiamonds that favors superlubricity, for which we will first develop a reactive force field properly describing interactions between C, Mo and S that matches ab-initio simulation results, and move on to superlubricity test by MD simulations to study phase transition and lubricity. This project uses VASP for ab-initio simulations and LAMMPS for MD. Both codes are proven to work efficiently on parallel processors. VASP scales with CPUs up to 64 CPUs. LAMMPS scales linearly with number of processors up to 200-300 atoms per processor. Industry partnership: Project URL: Requested allocation: 400000 Q1: 0 Q2: 0 Q3: 0 Q4: 400000 Justification: Storage requirements: The requester has used undetermined amount hours of their initial startup project. In addition to approving an initial amount, please specify a Category and Subcategory for this project. For a list of the current selection of approved categories, please see: https://wiki.lcrc.anl.gov/wiki/Processes/Categories Once the Allocation committee has approved the project, please go to the Project Management page to create it: https://accounts.lcrc.anl.gov/projects.php Thank You, The LCRC Accounts System