The mechanisms underlying the deformation of nanovoids in Ta single crystals are analyzed when they are subjected to cyclic uniaxial deformation using numerical simulations. Boundary and cell-size effects have been mitigated by means of the Quasicontinuum (QC) method. We have considered {approx} 1 billion-atom systems containing 10.9 nm voids. Two kinds of simulations have been performed, each characterized by a different boundary condition. First, we compress the material along the nominal [0 0 1] direction, resulting in a highly symmetric configuration that results in high stresses. Second, we load the material along the high-index [{bar 4}819] direction to confine plasticity to a single slip system and break the symmetry. We find that the plastic response under these two conditions is strikingly different, the former governed by dislocation loop emission and dipole formation, while the latter is dominated by twinning. We calculate the irreversible plastic work budget derived from a loading-unloading cycle and identify the most relevant yield points. These calculations represent the first fully three-dimensional, fully non-local simulations of any body-centered cubic metal using QC.

Lithium batteries are important as the power source for portable electronic devices and could also be used in hybrid vehicles with improvements in capacity. We have used first principles calculations of electronic structure to determine how charge is redistributed as Li is added or removed. In the final of year of the project we have examined Lix(NiMn)0.5O2 and Lix(NiMnCo)0.333O2 cathode materials in more detail. As lithium is removed electrons are removed from the valence band which is mainly Oxygen 2p states at the top of the band. There is very little change in the charge state of the transition element ions in either case. These results are confirmed by electron energy loss spectroscopy which shows a pre-peak on the oxygen K edge as lithium is removed, but no changes in the transition metal L edges. We have also investigated the LixFePO4 cathode material which is less costly than the LixCoO2 used at present and is also less damaging to the environment. In this case we find that as lithium is removed there is a change in charge state of iron while electrons are removed from oxygen 2p states at the top of the valence band. Again this is confirmed by …

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We summarize the latest results from performing Lattice QCD calculations with two different discretization schemes, asqtad and p4fat3, on the LLNL BG/L supercomputer, and present a plan for continued running to complete the calculation of the QCD transition temperature and equation of state.