We observe using ab initio methods that localized surface plasmon resonances in icosahedral silver nanoparticles enter the asymptotic region already between diameters of 1-2 nm, converging close to the classical quasistatic limit around 3.4 eV. We base the observation on time-dependent densityfunctional theory simulations of the icosahedral silver clusters Ag55 (1.06 nm), Ag147 (1.60 nm), Ag309 (2.14 nm), and Ag561 (2.68 nm). The simulation method combines the adiabatic GLLB-SC exchange-correlation functional with real time propagation in an atomic orbital basis set using the projector augmented wave method. The method has been implemented to the electron structure code GPAW within the scope of this work. We obtain good agreement with experimental data and modelled results, including photoemission and plasmon resonance. Moreover we can extrapolate the ab initio results to the classical quasistatically modelled icosahedral clusters.

We report the oxygen K-edge spectra of ices Ih, VI, VII, and VIII measured with X-ray Raman scattering. The pre-edge and main-edge contributions increase strongly with density, even though the hydrogen bond arrangements are very similar in these phases. While the near-edge spectral features in water and ice have often been linked to hydrogen bonding, we show that the spectral changes in the phases studied here can be quantitatively related to structural changes in the second coordination shell. Density-functional theory calculations reproduce the experimental results and support the conclusion. Our results suggest that non-hydrogen-bonded neighbors can have a significant effect also in the liquid water spectrum. We discuss the implications of the results for the actively debated interpretation of the liquid water spectrum in terms of local structure.