title: Electronic Energy Levels and Band Alignment for Aqueous Phenol and Phenolate from First Principles.
abstract: Electronic energy levels in phenol and phenolate solutions have been computed using density functional theory and many-body perturbation theory. The valence and conduction bands of the solvent and the ionization energies of the solutes have been aligned with respect to the vacuum level based on the concept of a computational standard hydrogen electrode. We have found significant quantitative differences between the generalized-gradient approximation, calculations with the HSE hybrid functional, and many-body perturbation theory in the G0W0 approximation. For phenol, two ionization energies below the photoionization threshold of bulk water have been assigned in the spectrum of Kohn-Sham eigenvalues of the solution. Deprotonation to phenolate was found to lift a third occupied energy level above the valence band maximum of the solvent which is characterized by an electronic lone pair at the hydroxyl group. The second and third ionization energies of phenolate were found to be very similar and explain the intensity pattern observed in recent experiments using liquid-microjet photoemission spectroscopy.
authors.affiliation: †Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Opalka
authors.affiliation: ‡Lawrence Livermore National Laboratory, Livermore, California 94551, United States.
authors.forename: Tuan Anh
authors.initials: TA
authors.lastname: Pham
authors.affiliation: §Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, United Kingdom.
authors.forename: Michiel
authors.initials: M
authors.lastname: Sprik
authors.affiliation: ∥The Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States.
authors.forename: Giulia
authors.initials: G
authors.lastname: Galli