| 1. |
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| 2. |
- Lüder, J., et al.
(författare)
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Electronic correlations revealed by hybrid functional and GW calculations in the anti-aromatic biphenylene molecule
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The biphenylene molecule is an interesting new candidate as a building block for advanced 2D materials. In this study, the molecular properties of biphenylene, like ionization potential and electron affinity, as well as the HOMO-LUMO gap were computed with the GW approach and with hybrid functional Density Functional Theory. B3LYP, HSE and HSE06 were compared as well as with the OT-RSH approach. The electronic structure of the valence states obtained by GW calculations and hybrid functionals was compared to experimental valence photoelectron spectroscopy data.
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| 3. |
- Lüder, J., et al.
(författare)
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Theory of X-ray spectroscopy of strongly correlated systems
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- X-ray absorption spectroscopy measured at the L-edge of transition metals (TMs) is a powerful element-selective tool providing direct information about the correlation effects in the 3d states. The theoretical modelling of the 2p to 3d excitation processes remains a challenge for contemporary ab initio electronic structure techniques, due to strong core-hole and multiplet effects influencing the spectra. In this work we present a realisation of the method combining the density functional theory with multiplet ligand field theory, proposed in Phys. Rev. B 85, 165113 (2012). The core of this approach is the solution of the single-impurity Anderson model (SIAM), parameterised from first principles.In our implementation, we adopt the dynamical mean-field theory and utilize the local Hamiltonian and the hybridisation function, projected onto TM 3d states, in order to construct the SIAM. We show that the current method can be used as an alternative to the construction of the Wannier functions. The developed computational scheme is applied to calculate the L-edge spectra for several TM monoxides. An excellent agreement between the theory and experiment is found for all studied systems. The possible extensions of the method as well as its limitations are discussed.
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| 4. |
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| 5. |
- Andersson, S, et al.
(författare)
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CO dissociation characteristics on size-distributed rhodium islands on alumina model substrates
- 1998
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Ingår i: JOURNAL OF CHEMICAL PHYSICS. - : AMER INST PHYSICS. - 0021-9606. ; 108:7, s. 2967-2974
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The dissociation of CO on size-distributed Rh particles supported on a thin alumina film has been studied with high resolution X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS). Adsorbed CO dissociates upon heating to temperat
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| 6. |
- Andersson, S, et al.
(författare)
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Metal-oxide interaction for metal clusters on a metal-supported thin alumina film
- 1999
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Ingår i: SURFACE SCIENCE. - : ELSEVIER SCIENCE BV. ; 442:1
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The interaction between deposited metal clusters and a thin model alumina film grown on NiAl(110) have been studied using X-ray absorption spectroscopy (XAS) and core and valence photoelectron spectroscopy. A lower limit for the fundamental gap of the sup
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| 7. |
- Andersson, S, et al.
(författare)
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Temperature dependent XPS study of CO dissociation on small Rh particles
- 1998
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Ingår i: VACUUM. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0042-207X. ; 49:3, s. 167-170
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We have used temperature dependent X-ray Photoelectron Spectroscopy (XPS) to study the heating-induced CO dissociation on oxide-supported Rh particles through observation of changes undergone by the adsorbate CO and the formation of atomic carbon from the
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| 8. |
- Bidermane, Ieva, 1984-, et al.
(författare)
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Atomic Contributions to the Valence Band Photoelectron Spectra of Metal-free, Iron and Manganese Phthalocyanines
- 2015
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 205, s. 92-97
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Forskningsöversikt (övrigt vetenskapligt/konstnärligt)abstract
- The present work reports a photoelectron spectroscopy study of the low-energy region of the valence band of metal-free phthalocyanine (H2Pc) compared with those of iron phthalocyanine (FePc) and manganese phthalocyanine (MnPc). We have analysed in detail the atomic orbital composition of the valence band both experimentally, by making use of the variation in photoionization cross-sections with photon energy, and theoretically, by means of density functional theory. The atomic character of the Highest Occupied Molecular Orbital (HOMO), reflected on the outermost valence band binding energy region, is different for MnPc as compared to the other two molecules. The peaks related to the C 2p contributions, result in the HOMO for H2Pc and FePc and in the HOMO-1 for MnPc as described by the theoretical predictions, in very good agreement with the experimental results. The DFT simulations, discerning the atomic contribution to the density of states, indicate how the central metal atom interacts with the C and N atoms of the molecule, giving rise to different partial and total density of states for these three Pc molecules.
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| 9. |
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| 10. |
- Frank, M, et al.
(författare)
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Particle size dependent CO dissociation on alumina-supported Rh: a model study
- 1997
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Ingår i: CHEMICAL PHYSICS LETTERS. - : ELSEVIER SCIENCE BV. - 0009-2614. ; 279:1-2, s. 92-99
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Via deposition of Ph from the gas phase onto a thin, well-ordered alumina film we have prepared various of alumina-supported Rh particle systems. The morphologies and particle sizes have been characterised with spot profile analysis LEED and STM measureme
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| 11. |
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| 12. |
- Gopakumar, Geethanjali, 1992-, et al.
(författare)
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X-ray Induced Fragmentation of Protonated Cystine
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Protein structure determination using high-intensity X-ray sources induces damage in the protein. Disulfide bridges, formed between two cysteine amino acid residues stabilize the protein structure. Owing to the higher absorption cross-section of sulfur for X-ray photons, and a large number of electrons released from sulfur atoms, these disulfide bridges are hot spots for a higher level of noise in structural studies. But it is yet to be understood how exactly the damage occurs through the interaction of the disulfide bridges with photons. Here we study the fragmentation of protonated cystine in the gas phase, which is the dimer of cysteine, by irradiation with X-rays across the sulfur L-edge using an electrospray ionization source (ESI) in combination with an ion trap. This is complemented with the calculation of the sulfur NEXAFS spectrum on the level of Restricted Open-Shell Configuration Interaction (ROCIS) and Density Functional Theory (DFT) calculations for molecular orbital visualization as well as Molecular Dynamics (MD) simulations for the fragmentation of triply charged cystine ions. We have deduced a possible pathway of fragmentation upon excitation and ionization of S 2p electrons by combining the experiments and simulations. The disulfide bridge breaks for resonant excitation at lower energies but remains intact upon higher energy resonant excitation and upon ionization of S 2p. The larger fragments formed subsequently break into smaller fragments.
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| 13. |
- Klar, D., et al.
(författare)
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Oxygen-tuned magnetic coupling of Fe-phthalocyanine molecules to ferromagnetic Co films
- 2013
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 88:22, s. 224424-
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Tidskriftsartikel (refereegranskat)abstract
- The coupling of submonolayer coverages of Fe-phthalocyanine molecules on bare and oxygen-covered ferromagnetic Co(001) films was studied by x-ray-absorption spectroscopy, especially the x-ray magnetic circular dichroism, in combination with density functional theory. We observe that the magnetic moments of the paramagnetic molecules are aligned even at room temperature, resulting from a magnetic coupling to the substrate. While the magnetization of the Fe ions directly adsorbed on the Co surface is parallel to the magnetization of the Co film, the introduction of an oxygen interlayer leads to an antiparallel alignment. As confirmed by theory, the coupling strength is larger for the system FePc/Co than for FePc/O/Co, causing a stronger temperature dependence of the Fe magnetization for the latter system. Furthermore, the calculations reveal that the coupling mechanism changes due to the O layer from mostly direct exchange to Co of the bare surface to a 180 degrees antiferromagnetic superexchange via the O atoms. Finally, by comparing the experimental x-ray-absorption spectra at the N K edge with the corresponding calculations, the contribution of the individual orbitals has been determined and the two inequivalent N atoms of the molecules could be distinguished.
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| 14. |
- Ogasawara, H., et al.
(författare)
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Structure and Bonding of Water on Pt(111)
- 2002
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Ingår i: Physical Review Letters. - : American Physical Society. - 1079-7114. ; 89:27, s. 276102-276105
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Tidskriftsartikel (refereegranskat)abstract
- We address the adsorption of water on Pt(111) using x-ray absorption, x-ray emission, and x-ray photoelectron spectroscopy along with calculations in the framework of density functional theory. Using the direct relationship between the electronic structure and adsorbate geometry, we show that in the first layer all the molecules bind directly to the surface and to each other through the in-layer H bonds without dissociation, creating a nearly flat overlayer. The water molecules are adsorbed through alternating metal-oxygen (M-O) and metal-hydrogen (M-HO) bonds.
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| 15. |
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| 16. |
- Snezhkova, O., et al.
(författare)
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Iron phthalocyanine on copper nitride: geometry, spin state, and modification by pyridine adsorption
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Using a monolayer of iron phthalocyanine adsorbed on the Au(111) surface and on a Cu(111)-supported two-dimensional copper nitride layer, we show how the modification of the support can influence the electronic and magnetic properties of an adsorbed transition metal complex. The two systems have been studied by a combination of electron spectroscopy and first principles theoretical calculations, which included modelling of the van der Waals interactions. For adsorption of iron phthalocyanine on the Cu(100)c(2x2)-2N/Cu(111) surface we find several different adsorbate structures at different surface sites, which all have very similar energies. Depending on the adsorption site - above a support nitrogen or a support copper atom - the spin magnetic moment of the molecular iron ion assumes different values. Although pyridine adsorption on the iron phthalocyanine monolayer reduces the spin magnetic moments for all phthalocyanine adsorption sites, the difference between the different sites persists: only for the iron phthalocyanine adsorbates with the central iron ion above a support nitrogen atom the spin is quenched completely, while a residual spin magnetic moment is found for the adsorption structures with the iron ion above a copper atom. The results illustrate clearly the relevance of the support as a ligand to the central ion.
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| 17. |
- Totani, R., et al.
(författare)
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Core levels, valence band structures and unoccupied states of biphenylene films
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Biphenylene is a cyclic hydrocarbon made of two benzene rings connected by a cyclobutadiene ring. We performed a photoemission and near-edge absorption (PES and NEXAFS) spectroscopy investigation on biphenylene films of different thicknesses, deposited onto a Cu(111) crystal. By PES we studied the occupied core and valence levels, while NEXAFS gave us information on the unoccupied states. The obtained results have been compared to previous gas phase spectra and density functional theory (DFT) calculations on single biphenylene molecule to get insights in the film electronic structure and possible modification induces by the adsorption. Furthermore, NEXAFS results of biphenylene films of different thicknesses allowed the characterization of the molecular arrangement in the overlayer on the Cu surface and helped to clarify the substrate-molecule interactions.
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| 18. |
- Totani, R., et al.
(författare)
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Electronic structure investigation of biphenylene films
- 2017
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Ingår i: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 146:5
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Tidskriftsartikel (refereegranskat)abstract
- Photoelectron Spectroscopy (PS) and Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy have been used to investigate the occupied and empty density of states of biphenylene films of different thicknesses, deposited onto a Cu(111) crystal. The obtained results have been compared to previous gas phase spectra and single molecule Density Functional Theory (DFT) calculations to get insights into the possible modification of the molecular electronic structure in the film induced by the adsorption on a surface. Furthermore, NEXAFS measurements allowed characterizing the variation of the molecular arrangement with the film thickness and helped to clarify the substrate-molecule interaction. Published by AIP Publishing.
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| 19. |
- Zhang, Teng, et al.
(författare)
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Conclusively Addressing the CoPc Electronic Structure : A Joint Gas-Phase and Solid-State Photoemission and Absorption Spectroscopy Study
- 2017
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 121:47, s. 26372-26378
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Tidskriftsartikel (refereegranskat)abstract
- The occupied and empty densities of states of cobalt phthalocyanine (CoPc) were investigated by photoelectron and X-ray absorption spectroscopies in the gas phase and in thin films deposited on a Au(111) surface. The comparison between the gas-phase results and density functional theory single-molecule simulations confirmed that the CoPc ground state is correctly described by the (2)A(1g) electronic configuration. Moreover, photon-energy-dependent valence photoemission spectra of both the gas phase and thin film confirmed the atomic character of the highest occupied molecular orbital as being derived from the organic ligand, with dominant contributions from the carbon atoms. Multiplet ligand-field theory was employed to simulate the Co L-edge X-ray absorption spectroscopy results.
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