A consistent dielectric response model for water ice over the whole energy–momentum plane

Semi-empirical dielectric descriptions of the Bethe surface of the valence bands of condensed water

“…A Drude-type parameterization of the experimental optical data of liquid and solid water (hexagonal and amorphous ice) has been presented in detail elsewhere [14,16] and briefly discussed here following Eq. (6).…”

“…k = 2.84 and 5.71 Å À1 ) as obtained from the dielectric models examined and the experimental IXS data for liquid water [18] which are reported to have insignificant uncertainties. The FED model calculations [14,16] pertain to both the liquid and solid phase (same dispersion formulae for both phases but different optical data) whereas all other calculations are limited to the liquid phase. As expected, differences between the three forms of condensed water are small and decrease with momentum transfer.…”

“…Recent applications of the above version of the Ritchie and Howie model may be found in Leger et al [19], Akkerman et al [20] and Tung et al [21]. For condensed water, the availability of experimental data for all dielectric function representations, namely, ReðeÞ ¼ e 1 ; ImðeÞ ¼ e 2 and Im À1=e ð Þ, has motivated the development of somewhat more elaborate representations of its dielectric response properties where basic band structure characteristics are accounted for [12][13][14][15][16]22]. In the study of liquid [12][13][14][15] and solid [16] water the following set of equations has been adopted to represent the experimental data.…”

“…The B excit,min is taken at 7-8 eV (corresponding to the photoabsorption threshold or the band gap). The values of the Drude coefficients f j , E j and c j for each valence band transition in liquid and solid water may be found in [14] and [16], respectively. The consistency of the ''fitting" procedure is ensured by the fulfillment (to within 1%) of the following sum rules for the normalized number of valence electrons:…”

“…With respect to condensed water, Emfietzoglou and coworkers [12][13][14][15][16] have provided a comprehensive review and intercomparison of various extended-optical-data models and advanced an improved scheme for both the liquid and solid phase [14,16]. The new development is based on an effective parameterization of the available inelastic X-ray scattering (IXS) data [17,18] by means of a fullyextended-Drude (FED) model in the Ritchie and Howie sense.…”