Interplay between elastic fields due to gravity and a partial dislocation for a hard-sphere crystal coherently grown under gravity: driving force for defect disappearance

We previously observed that an intrinsic staking fault shrunk through a glide of a Shockley partial dislocation terminating its lower end in a hard-sphere crystal under gravity coherently grown in by Monte Carlo simulations [Mori et al., Molec. Phys. 105, 1377 (2007)]; it was an answer to a one-decade long standing question why the stacking disorder in colloidal crystals reduced under gravity [Zhu et al., Nature 387, 883 (1997)]. Here, we present an elastic energy calculation; in addition to the self-energy of the partial dislocation [Mori et al., Prog. Theor. Phys. Suppl. 178, 33 (2009)] we calculate the cross-coupling term between elastic field due to gravity and that due to a Shockley partial dislocation. The cross term is a increasing function of the linear dimension R over which the elastic field expands, showing that a driving force arises for the partial dislocation moving toward the upper boundary of a grain.Comment: 8pages, 4figures, to be published in Molecular Physic

Study of corrosion of 1100 aluminum

Corrosion of 1100 aluminum in oxygen-saturated water at 70 degrees C under experimental conditions was studied, emphasizing effects of exposure interruption, the number of specimens, and the refreshment rate. A logarithmic equation was derived to express the corrosion rate

Study of crevice-galvanic corrosion of aluminum

Corrosion effects of aluminum-copper and aluminum-nickel couples in oxygenated distilled water, and aluminum alloys in oxygenated copper sulfate solution were studied. One of each of the couples had a water tight seal, and showed no substantial corrosion, and of the unsealed couples, only the aluminum-copper developed corrosion

The discontinuous nature of the exchange-correlation functional -- critical for strongly correlated systems

Standard approximations for the exchange-correlation functional have been found to give big errors for the linearity condition of fractional charges, leading to delocalization error, and the constancy condition of fractional spins, leading to static correlation error. These two conditions are now unified for states with both fractional charge and fractional spin: the exact energy functional is a plane, linear along the fractional charge coordinate and constant along the fractional spin coordinate with a line of discontinuity at the integer. This sheds light on the nature of the derivative discontinuity and calls for explicitly discontinuous functionals of the density or orbitals that go beyond currently used smooth approximations. This is key for the application of DFT to strongly correlated systems.Comment: 5 pages 2 figure

Transverse self-modulation of ultra-relativistic lepton beams in the plasma wakefield accelerator

The transverse self-modulation of ultra-relativistic, long lepton bunches in high-density plasmas is explored through full-scale particle-in-cell simulations. We demonstrate that long SLAC-type electron and positron bunches can become strongly self-modulated over centimeter distances, leading to wake excitation in the blowout regime with accelerating fields in excess of 20 GV/m. We show that particles energy variations exceeding 10 GeV can occur in meter-long plasmas. We find that the self-modulation of positively and negatively charged bunches differ when the blowout is reached. Seeding the self-modulation instability suppresses the competing hosing instability. This work reveals that a proof-of-principle experiment to test the physics of bunch self-modulation can be performed with available lepton bunches and with existing experimental apparatus and diagnostics.Comment: 8 pages, 8 figures, accepted for publication in Physics of Plasma