title: Electronic structure effects from hydrogen bonding in the liquid phase and in chemisorption: an integrated theory and experimental effort.
abstract: A closely integrated theoretical and experimental effort to understand chemical bonding using X-ray spectroscopic probes is presented. Theoretical techniques to simulate XAS (X-ray absorption spectroscopy), XES (X-ray emission spectroscopy), RIXS (resonant inelastic X-ray scattering) and XPS (X-ray photoelectron spectroscopy) spectra have been developed and implemented within a density functional theory (DFT) framework. In combination with new experimental techniques, such as high-resolution XAS on liquid water under ambient conditions and XES on complicated surface adsorbates, new insight into e.g. hydrogen-bonded systems is obtained. For the (3x2) overlayer structure of glycine/Cu(110), earlier work has been extended to include adsorbate-adsorbate interactions. Structures are optimized for large cluster models and for periodic boundary conditions. It is found that specific features in the spectra arise from hydrogen-bonding interactions, which thus have important effects at the molecular-orbital level. XAS on liquid water shows a pronounced pre-edge feature with significant intensity, while the spectrum of ice shows only little intensity in this region. Theoretical spectrum calculations, based on instantaneous structures obtained from molecular-dynamics (MD) simulations, show that the pre-edge feature in the liquid is caused by water molecules with unsaturated hydrogen bonding. Some aspects of the theoretical simulations will be briefly discussed.
authors.affiliation: FYSIKUM, University of Stockholm, Sweden. lgm@physto.se
authors.forename: L G
authors.initials: LG
authors.lastname: Pettersson
authors.forename: A
authors.initials: A
authors.lastname: Nilsson
authors.forename: S
authors.initials: S
authors.lastname: Myneni
authors.forename: Y
authors.initials: Y
authors.lastname: Luo
authors.forename: M
authors.initials: M
authors.lastname: Nyberg
authors.forename: M
authors.initials: M
authors.lastname: Cavalleri
authors.forename: L
authors.initials: L
authors.lastname: Ojamäe
authors.forename: L A
authors.initials: LA
authors.lastname: Näslund
authors.forename: H
authors.initials: H
authors.lastname: Ogasawara
authors.forename: M
authors.initials: M
authors.lastname: Odelius
authors.forename: A
authors.initials: A
authors.lastname: Pelmenschikov