USING CLUSTER STUDIES TO APPROACH THE ELECTRONIC-STRUCTURE OF BULK WATER - REASSESSING THE VACUUM LEVEL, CONDUCTION-BAND EDGE, AND BAND-GAPOF WATER

Aqueous cluster studies have lead to a reassessment of the electronic properties of bulk water, such as band gap, conduction band edge, and vacuum level. Using results from experimental hydrated electron cluste r studies, the location of the conduction band edge relative to the Va cuum level (often called the V-0 value) in water has been determined t o be -0.12 eV less than or equal to V-0 less than or equal to 0.0 eV, which is an order of magnitude smaller than most experimental values i n the literature. With V-0 = -0.12 eV and making use of the calculated solvation energy of OH in water, the band gap of water is determined to be 6.9 eV. Again, this is smaller than many literature estimates. I n the course of this work, it is shown that due to water's ability to reorganize about charge (1) photoemission thresholds of water or anion ic defects in water do not determine the vacuum level, and (2) then is almost no probability of accessing the bottom of the conduction band of water with a vertical/optical process from water's valence band. Th e results are presented in an energy diagram for bulk water which show s the utility of exploring the conduction band of water as a function of solvent polarization. (C) 1997 American Institute of Physics.