Electron energy spectrum of ice

Abstract

For the first time the tight-binding model and the recursion method are used to study the electron energy spectrum of hexagonal ice (h ), which is characterized by disorder in its protonic subsystem. It is shown that, if the ice rules are fulfilled, the local density of states (LDOS) does not depend upon the proton configuration, but the violation of ice rules results in the strong disturbances of LDOS. Electron energy spectra of HaO + and OH ~ ions are also calculated.

Ab initio studies of quasi-one-dimensional pentagon and hexagon ice nanotubes

“…For bulk ice I h both calculations show that the DOS has a few singularity-like peaks due to the high degrees of degeneration at these values of energy. 19 In addition to the bandgap, we find the two Q1D ice nanotubes show nearly the same electron energy spectrum as that of ice I h except some small difference in fine peaks. We therefore tentatively conclude that the overall DOS features appear to be not very sensitive to the local hydrogen-bonding structure so long as the entire molecular system has long-range positional order.…”

“…Our calculated DOS for the bulk ice I h is in very good agreement with a previous theoretical calculation of electron energy spectrum for the proton-disordered ice I h . 19 In that work, the tight-binding approach was used for which a hopping matrix element was adjusted to fit the experimental bandgap 7.8 eV. For bulk ice I h both calculations show that the DOS has a few singularity-like peaks due to the high degrees of degeneration at these values of energy.…”

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

“…The excitation threshold, which corresponds to the onset of photoabsorption, was loosely associated with the band gap since the extrapolation of the experimental optical data to threshold may entail a relatively larger uncertainty. The band gap values chosen (7-8 eV) fall somewhere in the middle of the theoretical and experimental values found in the literature which vary between about 6 and 12 eV [40][41][42][43]. Finally, the adoption of the same band structure characteristics for the liquid and solid phases in terms of number and type of transitions and ionization thresholds, is also a reasonable approximation given that the same molecular orbitals persist in both phases, while [18] and model calculations with several extended-opticaldata dielectric models (see text).…”

Optical Absorption of Water: Coulomb Effects versus Hydrogen Bonding

“…The spectra of amorphous, hexagonal as well as cubic ice are dominated by a very pronounced first absorption peak at about 8.7 eV [1,2], while the absorption spectrum of the liquid shows a similar structure [3,4]. In the case of cubic ice, the first absorption peak was attributed to the calculated density of states [5]. However, the universal occurrence of the 8.7 eV peak in a variety of water phases suggests its molecular origin, as opposed to being due to specific transitions between electronic states arising from a crystalline structure with a particular symmetry.…”