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Excited States of Transition-Metal Complexes with Multi-Reference Linear Response Methods

Benjamin Helmich-Paris

Max-Planck-Institut für Kohlenforschung, Mülheim an der Ruhr, Germany

These days, calculations of excited states of open-shell molecules such as transition-metal complexes (TMC) are still a challenge for quantum chemical methods. For those systems, the competition of many sizable configurations in the wavefunction expansion requires the usage of multi-reference (MR) methods even when investigating the ground state only. The active-space orbitals from which all reference configurations are generated is still limited to 14-18 orbitals as it results in billions of configurations and keeps on growing exponentially. In practice, this is a severe limitation for excited-state calculations of TMC, in particular, with larger organic pi ligands.

In this talk, I will elaborate on MR linear-response (LR) approaches that are capable of describing both excitations within the active orbitals but additionally excitations involving core and virtual – non-active space orbitals.[1] So far, LR methods were not capable of describing excitations from (quasi-)degenerate open-shell ground states. To resolve this limitation, the LR formalism is applied to state-averaged CASSCF solutions for an ensemble of ground states, which has been recently developed in my group.

For small molecules and large active spaces, as in case of the permanganate ion, CASSCF-LR gives very good agreement with experiment and other formally more accurate wavefunction methods. Calculations on large TMC with minimal-active spaces, including only valence d orbitals, are feasible with CASSCF-LR, though, often give poor results in particular for charge-transfer CT excitations. CT excitations are often accompanied by large differential dynamic correlation. Current projects in my group to include dynamic correlation are outlined and their prospect is discussed.

[1] B. Helmich-Paris, J. Chem. Phys. 150, 174121 (2019)


Friday, 02. June 2023, 14.00

Hörsaal HS 10.01, Heinrichstraße 28, EG

Nanoscopic insights into the function of cell membranes

Georg Pabst

Biophysics, Institute of Molecular Biosciences, University of Graz

Biological membranes are fascinating multifunctional interfaces in and around cells. Transport, communication or various catalytic processes are examples of the diverse tasks of biological membranes, all of which are closely linked to the properties of this layer, which is only about five nanometres thick. How much physics is there in cell membranes? How do we gain physical insights into this dynamic interplay of thousands and thousands of molecules, and can we use them to develop new medicines?
We cordially invite you to a lecture from a research area between physics, biology, chemistry and medicine.

Wednesday, May 24 2023, 17:00
HS 05.12, Institute of Physics, Universitätsplatz 5, 1. Floor


Graz Advanced School of Science

Kareem Elsayad
Advanced Microscopy, Vienna Biocenter Core Facilities
Feeling Life with Light

The colour of light scattered from an object can give us information on its chemical consistency. For
example, a moldy apple will be a different colour to a fresh one. If we analyze the spectrum of colours
even more carefully and under special illumination conditions we can even identify individual chemical
constituents and their abundance. Less well known though is that it can also tell us about the objects'
mechanical properties - namely, how elastic and viscous it is. To do so however requires more
elaborate instruments for measuring the scattered lights' spectrum. I will talk about this, explaining
the principles of the scattering processes involved, and what they can and can't tell us. I will then go
on to describe some experiments in my lab, and how we have used this to understand how plant cells
grow to take on the shapes that they do, as a means for diagnosing the severity of COVID and
potentially long-COVID from blood plasma, and to uncover a hidden dynamic structure in the cell
nucleus that appears to coordinate genetic transcription.

Date: Tuesday, 16 May, 16:15
Location: Lecture Hall P2, Petersgasse 16, Graz University of Technology
Host: P. Banzer und M. Schultze
For a regularly updated colloquium program see: www.if.tugraz.at/colloquium.html

Tuneable Catalysts for Energy Conversion

C. Rameshan

Chair of Physical Chemistry, Montanuniversität Leoben

Perovskite oxides with their general structure ABO3 are an extremely versatile material class. They are stable at high temperatures even under harsh environments. Both A- and B-site of the host lattice can be doped, enabling a materials design approach (e.g., for utilization as electrode material, solar cell, catalyst or gas sensor). For our particular materials, their catalytic properties are optimized for catalytic and electrocatalytic energy conversion applications. Additionally, perovskite oxides can exsolve B-site cations under reducing conditions (i.e. the growth of finely dispersed nanoparticle on the surface). This feature makes them particularly interesting as novel catalyst materials for high temperature reactions.

In our work we highlight how we can tune the composition of different perovskites to optimize their surface and bulk properties. By a combination of spectroscopic (in-situ) characterization with theoretical calculations we can understand their specific properties. Especially the rich oxygen surface chemistry of these novel materials is responsible for the activation of CO2 and its further transformation in valuable products. Furthermore, perovskites can prevent some of the major problems of catalyst deactivation. The sintering of active nanoparticles and the deactivation by coke formation.

Friday, 12. May 2023, 14.00

Hörsaal HS 10.01, Heinrichstraße 28, EG

Investigating Interfacial Water Dynamics using Machine Learned Electron Densities

Alan Lewis

MPI Hamburg

Sum Frequency Generation (SFG) spectroscopy is a powerful experimental technique that can selectively probe the vibrational modes at water interfaces. However, interpreting SFG spectra often requires computationally expensive simulations, without which experimental results can be difficult to assign and understand. I introduce a new approach to calculating the interfacial dipole moments and polarizabilities needed to simulate the SFG spectrum, avoiding the need for a molecular decomposition of these properties and in principle enabling the simulation of water/solid interfaces. These calculations can be dramatically accelerated using our newly developed machine learning methods, which predict the electron density and the response of the electron density to a homogeneous field, avoiding the need for costly density functional theory and density functional perturbation theory calculations. This allows us to simulate the extremely long molecular dynamics trajectories required to converge SFG spectra, while including all contributions and correlations in the response of the interface.


Friday, 05. May 2023, 14.00

Hörsaal HS 10.01, Heinrichstraße 28, EG

Simulation of light at the nanoscale

Ulrich Hohenester

Institut of Physics, Karl-Franzens University Graz

Nano optics deals with light confinement at the nanoscale [1]. This is achieved by binding light to coherent surface excitations of nanostructures, these are surface plasmon polaritons for metallic nanostructures and surface phonon polaritons for ionic nanostructures. These resonances come along with strongly localized fields and allow squeezing light into extreme subwavelength volumes, which can be exploited for various applications such as sensing, surface enhanced Raman scattering (SERS), or metasurfaces.

In this talk I will give an introduction to the basic principles underlying nano optics and will discuss our simulation approach for light at the nanoscale, based on a boundary element method (BEM) approach, which has been successfully employed for the simulation of various experiments. In electron energy loss spectroscopy (EELS), we have visualized the three-dimensional photonic environment in an electron microscope [2]. In optofluidic force induction (OF2i), optical forces are employed for trapping and acceleration of nanoparticles in a microfluidic channel, which allows for an optical nanoparticle characterization scheme that achieves real-time optical counting with single-particle sensitivity and high throughput [3].

[1] U. Hohenester, Nano and Quantum Optics (Springer, Cham, 2020).

[2] M. Lagos et al., Nature 543, 533 (2017); X. Li et al., Science 371, 1364 (2021).

[3] M. Šimić et al., Phys. Rev. Appl. 18, 024056  (2022) ; ibid 19, 034041 (2023).


Friday, 28. April 2023, 14.00

Hörsaal HS 10.01, Heinrichstraße 28, EG

In March's NanoGraz meeting the doctoral candidates paid a visit to the Quantum Chemistry group of Prof. Adrian Daniel Boese. They were given an overview on what computational and theoretical chemistry is all about by Johannes Hoja (Senior Scientist) and Peter Hartmann (PhD candidate, organizer), as well as the specific research topics of the research group.
Fields such as the development of density functionals, inverse density functional theory and symmetry adapted perturbation theory were briefly presented, moving on to the challenging subject of crystal structure prediction (a special thanks goes to Johannes Hoja for taking the time to share his expertise on the matter).
The presentation was concluded by an introduction to what can be done with the methods at our disposal to aid experimentalists in the understanding and development of chemical reactions, be it the prediction of chemical reactivities,the unraveling of reaction mechanisms or processes occurring in solid state or on interfaces.
This was augmented by a crash-course on how to perform quantum mechanical calculations in practice and about the crucial steps involved.

We express our hope that the meeting will deepen the collaboration within the NanoGraz Doctoral Academy and has been an enriching experience for all attendees that will be of use to them in their future careers.

“Nanophotonics meet Optical Fibers: a flexible concept for single-virus sensing, achromatic light focusing and optical trapping”
Prof. Dr. Markus A. Schmidt
Leibniz Institute of Photonic Technology e.V. / Otto Schott Institute of Material Research Friedrich Schiller / University Jena ,Germany
HS 05.01, Experimentierhörsaal 04:15 - 05:15 p.m.
Tuesday 21 March 2023

meet the speaker coffee:
library Experimental Physics 03:45 – 04:15, Universitätsstraße 5, 1 OG

Optical fibers provide a waveguide platform with unique advantages, especially in the fields of bioanalytics and life sciences. In this talk, I will report our recent results on fibers (i) that are interfaced with nanostructures and (ii) that are used for the characterization of single-nanoobjects through nanoparticle tracking analysis. In detail, I will report on the optical trapping of microspheres and bacteria with only one single-mode fiber by interfacing nanoprinted meta-lenses with single-mode fiber. In addition, I will show that nanopillar-based metasurfaces can be interfaced with fiber for achromatic light focussing across the entire telecommunication range. I will also report on fibers that include longitudinal liquid filled nanochannels, used to characterize the diffusion of biologically-relevant nano-objects such as plasmonic nanospheres, artificial polymer beads or viruses through employing image-based tracking and mean-square displacement analysis.

Hydrogen Storage in Graphene

Stefan Heun

NEST, Istituto Nanoscienze-CNR and Scuola Normale Superiore, 56127 Pisa, Italy

The realization of innovative hydrogen storage materials has worldwide strategic importance. Graphene has recently attracted attention as a promising hydrogen storage medium. Indeed, graphene is lightweight, chemically stable, and exhibits attractive physical–chemical properties for hydrogen adsorption. Furthermore, the interaction between hydrogen and graphene can be controlled by functionalization.

In my seminar I will discuss various aspects of the interactions between hydrogen and graphene, like chemisorption, physisorption, and a combination of both, via the hydrogen spillover effect [1]. Then I will discuss the extension of these concepts to a new material, the three-dimensional arrangement of epitaxial graphene conformally grown on porousified crystalline SiC [2,3], that we have recently developed in collaboration with the group of U. Schmid from the TU Wien.


[1]        J.-W. Chen, S.-H. Hsieh, S.-S. Wong, Y.-C. Chiu, H.-W. Shiu, C.-H. Wang, Y.-W. Yang, Y.-J. Hsu, D. Convertino, C. Coletti, S. Heun, C.-H. Chen, and C.-L. Wu: Hydrogen spillover and storage on graphene with single-site Ti catalyst, ACS Energy Lett. 7 (2022) 2297 – 2303.

[2]        S. Veronesi, G. Pfusterschmied, F. Fabbri, M. Leitgeb, O. Arif, D. A. Esteban, S. Bals, U. Schmidt, S. Heun: 3D arrangement of epitaxial graphene conformally grown on porousified crystalline SiC, Carbon 189 (2022) 210 – 218.

[3]        A. Macili, Y. Vlamidis, G. Pfusterschmied, M. Leitgeb, U. Schmid, S. Heun, and S. Veronesi: Study of hydrogen absorption in a novel three-dimensional graphene structure: towards hydrogen storage applications, Appl. Surf. Sci. 615 (2023) 156375.


Friday, 17. March 2023, 14.00

Hörsaal HS 10.01, Heinrichstraße 28, EG

Chemistry Encaged: Clocking Electron Transfer Rates Inside Endofullerenes

Philip Moriarty, School of Physics & Astronomy, University of Nottingham

Remarkable advances in synthetic chemistry mean that fullerenes can now be partially ‘unzipped’, an atom or molecule placed inside, and the carbon framework subsequently zipped up again to restore the original cage architecture [1]. The resulting endofullerene represents both an exotic state of matter (in that the properties of the encapsulated species lie somewhere between those of the gas phase and the solid state) and a unique platform for the controlled study of intra- and intermolecular charge transfer. I will discuss unpublished results from our very recent beamtime experiments at the Diamond Light Source (Beamline I09, Feb 2023) in which we combined normal incidence X-ray standing wave (NIXSW) analysis [2] with the core-hole clock technique [3] to probe, in parallel, the influence of a substrate -- namely, Ag(111) -- on both the position of an encapsulated atom and the time it takes for an electron excited inside the cage to tunnel to the “outside world”.

[1] For a recent review of molecular surgery of this type, see S. Bloodworth and R. J. Whitby, Comm. Chem. 5 121 (2022)

[2] The key principles underpinning the NIXSW technique are described in DP Woodruff and DA Duncan, New J. Phys. 22 113012 (2020) For an overview of Beamline I09 and a non-technical introduction to NIXSW and endofullerenes, see Anatomy of a Physics Experiment

[3] Core-hole-clock spectroscopy is an energy-domain complement to ultrafast pump-probe spectroscopy and involves a comparison of X-ray absorption, Auger electron, resonant photoemission, and resonant Auger spectra to measure electron delocalisation/charge transfer times down to the femtosecond (and sub-femtosecond) regime. See P. A. Brühwiler, O. Karis, and N. Mårtensson, Rev. Mod. Phys. 74, 703 (2002) for an authoritative and engaging review.

Philip Moriarty is a Professor of Physics and EPSRC Established Career Fellow (2020-2025) in the School of Physics and Astronomy, University of Nottingham. His research interests span a number of topical themes in nanoscience with a particular focus on single atom/molecule manipulation using scanning probes, and the use of synchrotron-based spectroscopies for the analysis of the structural, chemical, and electronic properties of nanostructured/molecular systems. His ORCID profile has a full list of publications and grant awards. He has a keen interest in outreach activities, primary and secondary education, and both science and higher education funding policy. In addition to participating in a number of research council-funded public engagement projects (including Giants of the Infinitesimal), he has been interviewed, and written, for The Independent, The Guardian, Times Higher Education, BBC Radio 4, Die Zeit, and The Economist amongst others. Moriarty is also a regular contributor to the Sixty Symbols YouTube project, which was awarded the IOP’s Kelvin prize in 2016 for innovative and effective promotion of the public understanding of physics. He has taught undergraduate physics for twenty-five years and has always been struck by the number of students in his classes who profess a love of metal music and by the deep connections between heavy metal and quantum mechanics, as discussed in his first pop sci book, “When The Uncertainty Principle Goes To 11” (Ben Bella, 2018). He blogs at Symptoms Of The Universe.

Freitag, 10. März 2023, 14.00 Uhr

Hörsaal HS 10.01, Heinrichstraße 28, EG

The monthly meeting of the Doctoral Academy NanoGraz for February was held on Tuesday 28. In the meeting, Ph.D. students Masoud Hamidi and Diana Shakirova introduced the audience to finite-element simulations of electromagnetics problems, with a particular focus on efficient meshing of the simulation domain for chiral structures. Afterward, Dr. Adria Canos-Valero gave an insightful and engaging presentation on rotational behavior of electromagnetic fields at the interface of two dielectric media under total internal reflection condition.

Radiochemical effects of thermal neutron capture in coordination compounds

Jan M. Welch

Center for Labelling and Isotope Production (CLIP), TRIGA Center Atominstitut, TU Wien, Vienna,

 An extended tutorial-style introduction to applied radiochemistry and related concepts including nuclear (radioactive) decay and nuclear reactions and their electronic (chemical) consequences will be presented.  Special emphasis will be placed on 1) differences in the scale of nuclear and electronic (chemical) processes, 2) the nature and detection/quantification of decay radiation as a radiochemical tool and 3) the application of nuclear reactions (with thermal neutrons) to the production of useful radioisotopes.  The electronic (chemical) effects of nuclear reactions (thermal neutron capture) on coordination complexes of molybdenum(IV) (nitro, fluoro, methyl and unsubstituted molybdenum(IV)oxophthalocyanines; Figure below, left) and chromium(III) (Tris(2,2,6,6-tetramethyl-3,5-heptandionato)chromium(III); Figure below, right) and the application thereof to radioisotope production for medical and technical application will be discussed.  Finally, a short overview of prospective work and concepts in the area will be presented.


Freitag, 03. Februar 2023, 14.00 Uhr

Hörsaal HS 10.01, Heinrichstraße 28, EG

Sidestepping Kasha's rule in 2D semiconductors - excitons with negative-mass electrons

John M. Lupton

Institute of Experimental and Applied Physics, University of Regensburg, Regensburg, Germany

Novoselov and Geim pointed out early on that exfoliated monolayers of transition metal dichalcogenides are “essentially gigantic 2D molecules” (PNAS 2005). Owing to the extraordinary oscillator strength of mobile excitons, transitions can be identified which involve electrons in high-lying conduction bands. In effect, these transitions constitute a semiconductor analogue of absorption and fluorescence from the molecular S2 state – a violation Kasha’s emblematic rule.

Electrons in high-lying conduction bands have negative effective mass, giving rise to a unique progression of vibrational quanta in the photoluminescence. Unlike in most molecules, however, excitons in semiconductor monolayers can be driven at sufficiently high powers that they are coherently controlled and give rise to quantum interference phenomena such as electromagnetically induced transparency. In monolayer WSe2, for example, these high-lying excitons are characterized by narrow bands (<2 meV width) in a spectral range far above the bandgap, and make up an effective three-level quantum system with the bandgap exciton. Under electrical gating, UV-emitting trions form, exotic quasiparticles involving electrons of both positive and negative mass which emit circularly polarized light.

The electric-field dependence opens the possibility of tuning excitonic quantum interference for potential device applications. In addition, because of the further electronic confinement effects arising in twisted bilayer structures, the oscillator strength of high-lying species can be enhanced in stacked structures, opening up further avenues for tuneable excitonic quantum optics.

Freitag, 27. Jänner 2023, 14.00 Uhr

Hörsaal HS 10.01, Heinrichstraße 28, EG

The doctoral candidates of NanoGraz started the year by visiting the Pharmaceutical Technology group of Andreas Zimmer. They were introduced to the basics of what pharmaceutical technology and nanotechnology is about and then got to experience what lab work in this field is like.

One group learned about the methods of Dynamic Light Scattering, Differential Scanning Calorimetry, and Rheometry with which pharmaceutical systems are characterized. The other group took part in the manufacturing of tablets and suppositories and even got to bring their self-made suppositories with them home.

We hope that everyone had a nice time and that it will strengthen our collaboration in the future.

A special thank goes out to Bianca Seidl, Gabriele Kolany, Katharina Puskac, and Martin Reiser for giving the tours.



Phase transitions and behavior in organic semiconductor thin films

J. Novák 

Dept. of Condensed Matter Physics, Faculty of Science, Masaryk University, Kotlářská 2,
CZ-611 37, Brno, Czech Republic

The talk will deal with phase transitions and behavior of small molecule organic semiconductors (OSMs) as induced by various factors. At the beginning, I will give a short introduction to x-ray scattering techniques, which are main tools in the presented research, and physics and chemical nature of OSMs. Thereafter, individual cases of observed phase behavior will be discussed: (I) metal surface modification induced ultra-thin film phase and bulk phase orientation for para-sexiphenyl grown on Cu(110) surfaces; (II) thickness hindered β-phase nucleation and two-step phase transition observed for 5,11-bis(triethyl silylethynyl) anthradithiophene on amorphous substrates; (III) molecular mixing induced anisotropic ordering and smectic C phase appearance in pentacene-diindenorperylene binary mixture. Explanations for the observed behavior in the individual systems (I-III) will be provided based on substrate surface morphology and strain accumulation in molecular film; competition between entropy, molecules' steric properties, and anisotropic inter-molecular interactions; and competition between bulk and surface energy of molecular crystallites, respectively.

Freitag, 13. Jänner 2023, 14.00 Uhr

Hörsaal HS 10.01, Heinrichstraße 28, EG

History of Physics in Graz and Excursion to the UniGraz@Museum

The November 2022 meeting of the Doctoral Academy NanoGraz featured a journey into the history of physics at the University of Graz. The global impact of historical progress achieved at the University of Graz was contextualised. Dr. Klemens Rumpf, curator of the historical physics collection at the UniGraz@Museum ( https://universitaetsmuseen.uni-graz.at/de/unsere-sammlungen-und-ausstellungen/unigrazmuseum ), illuminated in his presentation the 438 years of continuous operations in the field of physics and natural sciences. Topics ranged from the Nobel laureates who worked at the University of Graz in the field of natural science to the formulation of the Stefan–Boltzmann law. A guided tour by Dr. Rumpf through the natural science section of the UniGraz@Museum included historical experiments and physics equipment used by various well known and famous scientists. Exhibits include rare items such as a filament electrometer of Victor Franz Hess (physics Nobel prize 1936) used to measure cosmic radiation, a telescope acquired in 1885 during the professorship of Ludwig Boltzmann and the first Styrian LASER constructed by Professor Aussenegg in 1964. Reproductions of historical experiments like Chladni plates, which illustrate vibrational modes and were first published in 1787, encouraged the participants to try out historic techniques hands-on.

Acknowledgments: Special thanks to Dr. Klemens Rumpf (Institute of Physics) and Mag. Franz Stangl (UniGraz@Museum)  for the support and access to the UniGraz@Museum.

Author: Thomas Boné

The NanoGraz monthly meetings kicked off in October with a tour of the OpNaQ group’s labs (Banzer group). NanoGraz members Johannes Bütow and Brian Kantor showcased their experimental setups while overviewing their work on structured light and its applications. With the diverse academic background of the NanoGraz members joining the meeting, a wealth of interesting topics were discussed.

In May 2022, we started a logo design competition to create a new and unifying corporate identity for the NanoGraz doctoral academy. Several very creative designs were submitted by the NanoGraz PhD candidates. Philipp Hurdax won the award (see photo) for the best logo design. Congratulations Philipp! The new NanoGraz logo will serve as an overarching symbol for our joint and interdisciplinary activities in the framework of the doctoral academy.

Philipp Hurdax recently finished his PhD thesis entitled "Charge Transfer Across Ultrathin Dielectric Layers: A Controlled Study of the Phenomenon on MgO on Ag(100)". Ultrathin dielectric films on metals have come into the focus of research due to their novel properties compared to both pristine metals and bulk dielectrics. They can decouple adsorbates from the underlying metal; however, they can also promote charge transfer into adsorbates. In his thesis, Philipp provided answers and the missing understanding of the phenomenon of charge transfer across dielectric interlayers both qualitatively and quantitatively, by using a combination of surface science techniques, including angular resolved photoemission spectroscopy and photoemission orbital tomography, which were supported by scanning tunneling microscopy experiments and density functional calculations. By controlling the preparation parameters of the dielectric/metal substrate, he was able to tune the charge transfer into adsorbates and demonstrated how the different electrostatic coupling of charged and uncharged species on the surface leads to surprising phenomena and affects the behavior of the molecular films in several interesting ways.


Univ.-Prof. Dr. Peter Banzer
+43 (0)316 380 - 8560

Univ.-Prof. Dr. Thomas Weiss
+43 (0)316 380 - 5228


Doctoral Academy NanoGraz: Functional Nanostructures in Physics, Chemistry and Life Sciences
Heinrichstraße 28/IV, 8010 Graz
Kogler Michaela, Schmid Sabine Phone:+43 (0)316 380 - 5510, 5410

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