BerkeleyGW is a massively parallel computational package for electron excitedstate properties that is based on many-body perturbation theory employing the ab initio GW and GW plus Bethe-Salpeter equation methodology. It can be used in conjunction with many density-functional theory codes for groundstate properties, including PARATEC, PARSEC, Quantum ESPRESSO, SIESTA, and Octopus. The package can be used to compute the electronic and optical properties of a wide variety of material systems from bulk semiconductors and metals to nanostructured materials and molecules. The package scales to 10000s of CPUs and can be used to study systems containing up to 100s of atoms.

We present the first experimental demonstration of zero backscattering from nanoparticles at optical frequencies as originally discussed by Kerker et al. [ Kerker , M. ; Wang , D. ; Giles , C. J. Opt. Soc. A 1983 , 73 , 765 ]. GaAs pillars were fabricated on a fused silica substrate and the spectrum of the backscattered radiation was measured in the wavelength range 600-1000 nm. Suppression of backscattering occurred at ~725 nm, agreeing with calculations based on the discrete dipole approximation. Particles with zero backscattering provide new functionality for metamaterials and optical antennas.

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