A phenomenological model is implemented to study the decay rates of fluorescing molecules in the vicinity of a metallic nanoparticle, wherein the nonlocal optical response of the particle is accounted for via the hydrodynamic model for the description of the free electrons in the metal. These nonlocal effects are examined for each of the radiative rate and the nonradiative rate of the admolecule, respectively. In addition, the overall fluorescence rate which includes the enhancement ratio for the driving field intensity is also studied. It is found that for particles of very small sizes (<10 nm), the nonlocal effects, in general, lead to significantly greater fluorescence rates and smaller nonradiative decay rates for the admolecules, with the effects on radiative rates depending crucially on the orientation of the molecules. Furthermore, the effects are mostly noticeable for molecules close to the metal particle and in processes where higher multipolar interactions are significant such as those in nonradiative decay processes. Above all, these nonlocal effects can still be observable in the presence of large surface damping imposed on the metallic electrons due to the ultrasmall sizes of these nanoparticles. The relevance of these effects to some of the latest experiments is discussed.

A shell model for ferroelectric perovskites fitted to results of first-principles density functional theory (DFT) calculations is strongly affected by approximations made in the exchange-correlation functional within DFT, and in general not as accurate as a shell model derived from experimental data. We have developed an isotropic shell model for BaTiO 3 based on the PBEsol exchange-correlation functional [Perdew et al., Phys. Rev. Lett. 100, 136406 (2008)], which was specifically designed for crystal properties of solids. Our shell model for BaTiO 3 agrees with ground state DFT properties and the experimental lattice constants at finite temperatures. The sequence of phases of BaTiO 3 (rhombohedral, orthorhombic, tetragonal, cubic) is correctly reproduced but the temperature scale of the phase transitions is compressed. The temperature scale can be improved by scaling of the ab-initio energy surface. V C 2013 AIP Publishing LLC. [http://dx.

The Department of Energy’s (DOE’s) National Energy Technology Laboratory’s (NETL’s) Blowout and Spill Occurrence Model (BLOSOM), and the National Oceanic and Atmospheric Administration’s (NOAA’s) General NOAA Operational Modeling Environment (GNOME) are compared. Increasingly complex simulations are used to assess similarities and differences between the two models’ components. The simulations presented here are forced by ocean currents from a Finite Volume Community Ocean Model (FVCOM) implementation that has excellent skill in representing tidal motion, and with observed wind data that compensates for a coarse vertical ocean model resolution. The comprehensive comparison between GNOME and BLOSOM presented here, should aid modelers in interpreting their results. Beyond many similarities, aspects where both models are distinct are highlighted. Some suggestions for improvement are included, e.g., the inclusion of temporal interpolation of the forcing fields (BLOSOM) or the inclusion of a deflection angle option when parameterizing wind-driven processes (GNOME). Overall, GNOME and BLOSOM perform similarly, and are found to be complementary oil spill models. This paper also sheds light on what drove the historical Point Wells spill, and serves the additional purpose of being a learning resource for those interested in oil spill modeling. The increasingly complex approach used for the comparison is also used, in parallel, to illustrate the approach an oil spill modeler would typically follow when trying to hindcast or forecast an oil spill, including detailed technical information on basic aspects, like choosing a computational time step. We discuss our successful hindcast of the 2003 Point Wells oil spill that, to our knowledge, had remained unexplained. The oil spill models’ solutions are compared to the historical Point Wells’ oil trajectory, in time and space, as determined from overflight information. Our hindcast broadly replicates the correct locations at the correct times, using accurate tide and wind forcing. While the choice of wind coefficient we use is unconventional, a simplified analytic model supported by observations, suggests that it is justified under this study’s circumstances. We highlight some of the key oceanographic findings as they may relate to other oil spills, and to the regional oceanography of the Salish Sea, including recommendations for future studies.

The p-type semiconductor Cu3PSe4 has recently been established to have a direct bandgap of 1.4 eV and an optical absorption spectrum similar to GaAs [Applied Physics Letters, 99, 181903 (2011)], suggesting a possible application as a solar photovoltaic absorber. Here we calculate the thermodynamic stability, defect energies and concentrations, and several material properties of Cu3PSe4 using a wholly GGA+U method (the generalized gradient approximation of density functional theory with a Hubbard U term included for the Cu-d orbitals). We find that two low energy acceptor defects, the copper vacancy VCu and the phosphorus-on-selenium antisite PSe, establish the p-type behavior and likely prevent any n-type doping near thermal equilibrium. The GGA+U defect calculation method is shown to yield more accurate results than the more standard method of applying post-calculation GGA+U -based bandgap corrections to strictly GGA defect calculations.