FY2010 - Oak Ridge National Laboratory

Seed Money Fund—
Physics Division
Statistical analysis of these simulations, for thousand of impacts per a point in parametric space
(energy, angle, particle, particle state), has led to the yields of the various dynamic processes, like
reflection, transmission, sputtering, and sticking. In addition, the potential of graphene was mapped
across the surface and the yields obtained were explained.
Using tight-binding Density Functional Theory (DFT), the change in electronic structure was detected
in the case of hydrogen molecules sticking to the graphehe sheet.
05869
Modeling of the Plasma-Material Interface
Predrag S. Krstic, Paul R. Kent, Jeffrey H. Harris, Donald Lee Hillis, Fred W. Meyer, and
Carlos O. Reinhold
Project Description
This project will develop an innovative theoretical-computational capability for simulations of processes
at the Plasma Material Interface (PMI) to help guide research on present and future linear and toroidal
PMI experiments. We envision development of a capability to build and validate predictive models for
both ion-beam-surface interactions and more complex plasma-surface interactions. The leading
component of the proposed research will be development of classical molecular dynamics interatomic
potentials for fusion-relevant composite surfaces (Li, C, H) and (W, C, H, He) and their validation with
the available experimental beam-surface interaction data. However, in case of Li-H-C (ionic solids) the
quantum-classical approach is attempted (based on the tight-binding Density Functional Theory) to
describe chemistry in the surface. In the transition to plasma irradiation studies, we will validate the
models using the existing data from the plasma PMI machines, like PISCES B (UCSD), NSTX (PPPL),
and beam surface experiments (Purdue).The work will provide a foundation for predictive science of the
PMI and will integrate theory with available plasma surface and beam surface measurements to validate
models for surface phenomena.
Mission Relevance
The walls of magnetic fusion reactors must sustain large particle and heat fluxes, which present a major
challenge to achieving controlled fusion power. A recent panel report to the Fusion Energy Sciences
Advisory Committee (FESAC07) found that of the top five critical knowledge gaps for fusion, four
involve the PMI. Fusion community REsearch NEeds Workshops (RENEW09) in 2009 have
recommended new PMI research programs and facilities to advance the science and technology of
plasma-surface interactions. A valid simulation of the plasma-material interface in the big fusion reactors
(ITER, DEMO) can save billions of dollars in the long term through a predictive scientific approach.
Understanding the effects of energetic particles on materials is of great relevance to the Department of
Defense (DOD), the National Aeronautics and Space Administration (NASA), and the Nuclear
Regulatory Commission (NRC).
Results and Accomplishments
Although the project has been active less than 6 months in FY 2010, great progress has been made on the
task for the first period, “Development and validation of potentials for the systems containing (Li, C, H).”
The principal challenge for mixed materials with lithium is strong polarization (due to the low
electronegativity of lithium in comparison to carbon and hydrogen), which in addition to the short-range
257