Evidence for ionic bonding in YH3-delta - art. no. 235502

The infrared transmission spectra of YH3-delta and YD3-delta thin films hav e been measured in the energy range from 300 to 6000 cm(-1), and the optica l constants have been calculated by Kramers-Kronig analysis. From a fit of the frequency-dependent conductivity and the dielectric loss functions with one Drude term and five Lorentz oscillators, the longitudinal and transver se optical-phonon frequencies have been determined. The Born and Szigeti ef fective charges have been calculated and the ionicities of the ions in YH3- delta have been derived. We find that hydrogen does not enter as a proton i n the compound, but that it is negatively charged, with a Szigeti effective charge of nearly 0.5e.