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BETA
Brena, Barbara
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Publications (10 of 58) Show all publications
Zhang, T., Brumboiu, I. E., Grazioli, C., Guarnaccio, A., Coreno, M., de Simone, M., . . . Puglia, C. (2018). Lone-Pair Delocalization Effects within Electron Donor Molecules: The Case of Triphenylamine and Its Thiophene-Analog. The Journal of Physical Chemistry C, 122(31), 17706-17717
Open this publication in new window or tab >>Lone-Pair Delocalization Effects within Electron Donor Molecules: The Case of Triphenylamine and Its Thiophene-Analog
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2018 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 31, p. 17706-17717Article in journal (Refereed) Published
Abstract [en]

Triphenylamine (TPA) and its thiophene-analog, N,N-diphenyl-2-thiophenamine (DPTA), are both well-known as electron-donating molecules implemented in optoelectronic devices such as organic solar cells and LEDs. Comprehensive valence and core level photoelectron spectroscopy, as well as near edge X-ray absorption spectroscopy (NEXAFS), measurements have been performed on gas phase TPA and DPTA. The experimental results have been compared to density functional theory calculations, providing a detailed description of the molecular electronic structure. Specifically, the C 1s photoelectron lines of both TPA and DPTA were resolved in the different C atom contributions and their binding energies explained as the result of two counter-acting effects: (1) the electronegativity of the nitrogen atom (and sulfur atom in DPTA) and (2) the the N (and S in DPTA) lone-pair electrons. In addition, the C K-edge NEXAFS spectrum of DPTA reveals that the lowest unoccupied molecular orbital (LUMO) energy position is affected differently if the core hole site is on the phenyl compared to the thiophene ring. The electron-donating properties of these two molecules are largely explained by the significant contribution of the N lone-pair electrons (p(z)) to the highest occupied molecular orbital. The contribution to the LUMO and to the empty density of states of the sulfur of the thiophene ring in DPTA explains the better performance of donor-pi-acceptor molecules containing this moiety and implemented in photoenergy conversion devices.

National Category
Physical Sciences Theoretical Chemistry Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-355118 (URN)10.1021/acs.jpcc.8b06475 (DOI)000441484600014 ()
Funder
Swedish Research Council, VR 2014-3776Carl Tryggers foundation
Note

Title in thesis list of papers: Lone Pair Delocalization Effect within Electron Donor Molecules:The Case of Triphenylamine (TPA) and Its Thiophene-Analog(DPTA)

Available from: 2018-06-29 Created: 2018-06-29 Last updated: 2018-10-15Bibliographically approved
Zhou, Y., Silva, J. L., Woods, J. M., Pondick, J. V., Feng, Q., Liang, Z., . . . Cha, J. J. (2018). Revealing the Contribution of Individual Factors to Hydrogen Evolution Reaction Catalytic Activity. Advanced Materials, 30(18), Article ID 1706076.
Open this publication in new window or tab >>Revealing the Contribution of Individual Factors to Hydrogen Evolution Reaction Catalytic Activity
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2018 (English)In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 30, no 18, article id 1706076Article in journal (Refereed) Published
Abstract [en]

For the electrochemical hydrogen evolution reaction (HER), the electrical properties of catalysts can play an important role in influencing the overall catalytic activity. This is particularly important for semiconducting HER catalysts such as MoS2, which has been extensively studied over the last decade. Herein, on-chip microreactors on two model catalysts, semiconducting MoS2 and semimetallic WTe2, are employed to extract the effects of individual factors and study their relations with the HER catalytic activity. It is shown that electron injection at the catalyst/current collector interface and intralayer and interlayer charge transport within the catalyst can be more important than thermodynamic energy considerations. For WTe2, the site-dependent activities and the relations of the pure thermodynamics to the overall activity are measured and established, as the microreactors allow precise measurements of the type and area of the catalytic sites. The approach presents opportunities to study electrochemical reactions systematically to help establish rational design principles for future electrocatalysts.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2018
Keywords
2D TMD materials, electrochemical microreactors, hydrogen evolution reaction, individual factors, overall performance
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-356393 (URN)10.1002/adma.201706076 (DOI)000431615100009 ()29573299 (PubMedID)
Funder
Swedish Research CouncilStandUp
Available from: 2018-07-25 Created: 2018-07-25 Last updated: 2018-07-25Bibliographically approved
Zhang, T., Brumboiu, I. E., Lanzilotto, V., Luder, J., Grazioli, C., Giangrisostomi, E., . . . Puglia, C. (2017). Conclusively Addressing the CoPc Electronic Structure: A Joint Gas-Phase and Solid-State Photoemission and Absorption Spectroscopy Study. The Journal of Physical Chemistry C, 121(47), 26372-26378
Open this publication in new window or tab >>Conclusively Addressing the CoPc Electronic Structure: A Joint Gas-Phase and Solid-State Photoemission and Absorption Spectroscopy Study
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2017 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 47, p. 26372-26378Article in journal (Refereed) Published
Abstract [en]

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.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-345249 (URN)10.1021/acs.jpcc.7b08524 (DOI)000417228500026 ()
Funder
Swedish Research CouncilCarl Tryggers foundation
Available from: 2018-03-09 Created: 2018-03-09 Last updated: 2018-03-09Bibliographically approved
Zhang, T., Brumboiu, I. E., Lanzilotto, V., Luder, J., Grazioli, C., Giangrisostomi, E., . . . Puglia, C. (2017). Conclusively Addressing the CoPc Electronic Structure: A Joint Gas-Phase and Solid-State Photoemission and Absorption Spectroscopy Study. The Journal of Physical Chemistry C, 121(47), 26372-26378
Open this publication in new window or tab >>Conclusively Addressing the CoPc Electronic Structure: A Joint Gas-Phase and Solid-State Photoemission and Absorption Spectroscopy Study
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2017 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 47, p. 26372-26378Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2017
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-344315 (URN)10.1021/acs.jpcc.7b08524 (DOI)000417228500026 ()
Funder
Swedish Research CouncilCarl Tryggers foundation
Available from: 2018-03-08 Created: 2018-03-08 Last updated: 2018-06-29Bibliographically approved
Totani, R., Grazioli, C., Zhang, T., Bidermane, I., Lüder, J., de Simone, M., . . . Puglia, C. (2017). Electronic structure investigation of biphenylene films. Journal of Chemical Physics, 146(5), Article ID 054705.
Open this publication in new window or tab >>Electronic structure investigation of biphenylene films
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2017 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 146, no 5, article id 054705Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2017
National Category
Chemical Sciences Physical Sciences
Identifiers
urn:nbn:se:uu:diva-320469 (URN)10.1063/1.4975104 (DOI)000394576600053 ()28178795 (PubMedID)
Available from: 2017-04-26 Created: 2017-04-26 Last updated: 2017-04-26Bibliographically approved
Lüder, J., Schött, J., Brena, B., Haverkort, M. W., Thunström, P., Eriksson, O., . . . Kvashnin, Y. (2017). Theory of L-edge spectroscopy of strongly correlated systems. Physical Review B, 96(24), Article ID 245131.
Open this publication in new window or tab >>Theory of L-edge spectroscopy of strongly correlated systems
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2017 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 24, article id 245131Article in journal (Refereed) Published
Abstract [en]

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 modeling of the 2p→3d excitation processes remains to be challenging for contemporary ab initio electronic structure techniques, due to strong core-hole and multiplet effects influencing the spectra. In this work, we present a realization of the method combining the density-functional theory with multiplet ligand field theory, proposed in Haverkort et al. [Phys. Rev. B 85, 165113 (2012)]. In this approach, a single-impurity Anderson model (SIAM) is constructed, with almost all parameters obtained from first principles, and then solved to obtain the spectra. In our implementation, we adopt the language of the dynamical mean-field theory and utilize the local density of states and the hybridization function, projected onto TM 3d states, in order to construct the SIAM. The developed computational scheme is applied to calculate the L-edge spectra for several TM monoxides. A very good agreement between the theory and experiment is found for all studied systems. The effect of core-hole relaxation, hybridization discretization, possible extensions of the method as well as its limitations are discussed.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-339767 (URN)10.1103/PhysRevB.96.245131 (DOI)000418573600012 ()
Funder
Knut and Alice Wallenberg Foundation, 2013.0020; 2012.0031Carl Tryggers foundation
Available from: 2018-02-02 Created: 2018-02-02 Last updated: 2018-10-10Bibliographically approved
Brumboiu, I. E., Prokopiou, G., Kronik, L. & Brena, B. (2017). Valence electronic structure of cobalt phthalocyanine from an optimally tuned range-separated hybrid functional. Journal of Chemical Physics, 147(4), Article ID 044301.
Open this publication in new window or tab >>Valence electronic structure of cobalt phthalocyanine from an optimally tuned range-separated hybrid functional
2017 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 147, no 4, article id 044301Article in journal (Refereed) Published
Abstract [en]

We analyse the valence electronic structure of cobalt phthalocyanine (CoPc) by means of optimally tuning a range-separated hybrid functional. The tuning is performed by modifying both the amount of short-range exact exchange (alpha) included in the hybrid functional and the range-separation parameter (gamma), with two strategies employed for finding the optimal gamma for each alpha. The influence of these two parameters on the structural, electronic, and magnetic properties of CoPc is thoroughly investigated. The electronic structure is found to be very sensitive to the amount and range in which the exact exchange is included. The electronic structure obtained using the optimal parameters is compared to gas-phase photo-electron data and GWcalculations, with the unoccupied states additionally compared with inverse photo-electron spectroscopy measurements. The calculated spectrum with tuned gamma, determined for the optimal value of alpha = 0.1, yields a very good agreement with both experimental results and with GW calculations that well-reproduce the experimental data.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-333518 (URN)10.1063/1.4993623 (DOI)000406347200011 ()28764387 (PubMedID)
Funder
Swedish Research Council, 2014-3776Knut and Alice Wallenberg Foundation, KAW-2013.0020
Available from: 2017-11-14 Created: 2017-11-14 Last updated: 2017-11-14Bibliographically approved
Bhandary, S., Schueler, M., Thunstroem, P., di Marco, I., Brena, B., Eriksson, O., . . . Sanyal, B. (2016). Correlated electron behavior of metal-organic molecules: Insights from density functional theory combined with many-body effects using exact diagonalization. PHYSICAL REVIEW B, 93(15), Article ID 155158.
Open this publication in new window or tab >>Correlated electron behavior of metal-organic molecules: Insights from density functional theory combined with many-body effects using exact diagonalization
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2016 (English)In: PHYSICAL REVIEW B, ISSN 2469-9950, Vol. 93, no 15, article id 155158Article in journal (Refereed) Published
Abstract [en]

A proper theoretical description of the electronic structure of the 3d orbitals in the metal centers of functional metalorganics is a challenging problem. We apply density functional theory and an exact diagonalization method in a many-body approach to study the ground-state electronic configuration of an iron porphyrin (FeP) molecule. Our study reveals that the consideration of multiple Slater determinants is important, and FeP is a potential candidate for realizing a spin crossover due to a subtle balance of crystal-field effects, on-site Coulomb repulsion, and hybridization between the Fe-d orbitals and ligand N-p states. The mechanism of switching between two close-lying electronic configurations of Fe-d orbitals is shown. We discuss the generality of the suggested approach and the possibility to properly describe the electronic structure and related low-energy physics of the whole class of correlated metal-centered organometallic molecules.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-297348 (URN)10.1103/PhysRevB.93.155158 (DOI)000374948400003 ()
Funder
Carl Tryggers foundation Swedish Research CouncilKnut and Alice Wallenberg FoundationeSSENCE - An eScience CollaborationGerman Research Foundation (DFG), FOR 1346
Available from: 2016-06-23 Created: 2016-06-22 Last updated: 2017-01-25Bibliographically approved
Brumboiu, I. E., Haldar, S., Luder, J., Eriksson, O., Herper, H. C., Brena, B. & Sanyal, B. (2016). Influence of Electron Correlation on the Electronic Structure and Magnetism of Transition-Metal Phthalocyanines. Journal of Chemical Theory and Computation, 12(4), 1772-1785
Open this publication in new window or tab >>Influence of Electron Correlation on the Electronic Structure and Magnetism of Transition-Metal Phthalocyanines
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2016 (English)In: Journal of Chemical Theory and Computation, Vol. 12, no 4, p. 1772-1785Article in journal (Refereed) Published
Abstract [en]

There exists an extensive literature on the electronic structure of transition-metal phthalocyanines (TMPcs), either as single molecules or adsorbed on surfaces, where explicit intra-atomic Coulomb interactions of the strongly correlated orbitals are included in the form of a Hubbard U term. The choice of U is, to a large extent, based solely on previous values reported in the literature for similar systems. Here, we provide a systematic analysis of the influence of electron correlation on the electronic structure and magnetism of several TMPcs (MnPc, FePc, CoPc, NiPc, and CuPc). By comparing calculated results to valence-band photoelectron spectroscopy measurements, and by determining the Hubbard term from linear response, we show that the choice of U is not as straightforward and can be different for each different TMPc. This, in turn, highlights the importance of individually estimating the value of U for each system before performing any further analysis and shows how this value can influence the final results.

National Category
Physical Sciences Materials Chemistry Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-281097 (URN)10.1021/acs.jctc.6b00091 (DOI)000374196400034 ()26925803 (PubMedID)
Funder
Swedish Research CouncilKnut and Alice Wallenberg Foundation
Available from: 2016-03-17 Created: 2016-03-17 Last updated: 2017-01-25Bibliographically approved
Lüder, J., Puglia, C., Ottosson, H., Eriksson, O., Sanyal, B. & Brena, B. (2016). Many-body effects and excitonic features in 2D biphenylene carbon. Journal of Chemical Physics, 144(2), Article ID 024702.
Open this publication in new window or tab >>Many-body effects and excitonic features in 2D biphenylene carbon
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2016 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 144, no 2, article id 024702Article in journal (Refereed) Published
Abstract [en]

The remarkable excitonic effects in low dimensional materials in connection to large binding energies of excitons are of great importance for research and technological applications such as in solar energy and quantum information processing as well as for fundamental investigations. In this study, the unique electronic and excitonic properties of the two dimensional carbon network biphenylene carbon were investigated with GW approach and the Bethe-Salpeter equation accounting for electron correlation effects and electron-hole interactions, respectively. Biphenylene carbon exhibits characteristic features including bright and dark excitons populating the optical gap of 0.52 eV and exciton binding energies of 530 meV as well as a technologically relevant intrinsic band gap of 1.05 eV. Biphenylene carbon's excitonic features, possibly tuned, suggest possible applications in the field of solar energy and quantum information technology in the future.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-278016 (URN)10.1063/1.4939273 (DOI)000368618400036 ()26772582 (PubMedID)
Funder
Knut and Alice Wallenberg Foundation
Available from: 2016-02-23 Created: 2016-02-23 Last updated: 2017-11-30Bibliographically approved
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