Online-Seminare der GDCh-Fachgruppe Festkörperchemie & Materialforschung

Die Fachgruppe Festkörperchemie & Materialforschung startete im Jahr 2021 eine Online-Vortragsreihe zur Förderung des wissenschaftlichen Austauschs auch über die derzeitige Corona-Pandemie hinaus durch ortsunabhängige, zweiwöchentliche Vorträge. Die Teilnahme ist kostenlos. Eine separate Registrierung für jedes Seminar ist erforderlich (Details siehe unten).

Dr. Sebastian Klemenz, Dr. Simon Steinberg, Dr. Christopher Benndorf,
Dr. Alexander Knebel, Jun.-Prof. Dr. Nathalie Kunkel

Online Seminar #8: Dr. Anna Isaeva

Dr. Anna Isaeva (Universiteit van Amsterdam)
June 22, 2021
6:00-7:30pm (Berlin time)

The seminar is free of charge, but REGISTRATION is needed!

"New Quantum Materials from Inorganic 2D Building Blocks: The Upswing of van der Waals Structures"
Layered compounds with van der Waals bonding are an attractive playground for materials design. The idea that promising compounds may be created by combining 2D layers with various functionalities (magnetic, electronic, optical, etc.) by stacking them in a periodic 3D crystal lattice is being actively explored by chemists, physicists and theorists alike. However, the whole is seldom a mere sum of the parts and the interlayer interactions in such materials are not as weak as they may seem at first. The layers often ‘see’ each other, and an interplay of their individual properties gives rise to novel phenomena. Thanks to the recent methodological and technological developments, materials science is now able to explore single van der Waals monolayers and discovers their unique magnetic, superconducting and transport properties originating from quantum effects. It is now also possible to trace how these properties evolve while transiting from 3D to 2D structures. These new possibilities attract many to the vibrant interdisciplinary research field on so called ‘van der Waals quantum materials’. While fully appreciating the prospects that layered materials hold for new chemistry and physics, one should not forget about the other side of the medal: the formation of competing polymorphs, or metastable, or poorly ordered phases with strong stacking disorder challenge the synthesis. I will give a brief overview of the nowadays most prominent van der Waals materials ‘beyond graphene’ (e.g. transition metal dichalcogenides, CrI3 and other magnetic 2D materials, 2D topological insulators and superconductors) and then focus on the family of (MnBi2Te4)(Bi2Te3)n, n = 0-3, layered compounds. They exhibit both magnetic and topological (quantized surface transport) properties that can be tuned by compositional and structural modifications.

Online Seminar #7: Dr. Hana Bunzen

Dr. Hana Bunzen (Universität Augsburg)
June 8, 2021
6:00-7:30pm (Berlin time)

The seminar is free of charge, but REGISTRATION is needed!

“Metal-organic frameworks for drug delivery in cancer therapy”
Delivering therapeutic agents in a sufficient concentration to a target site is a major challenge in the treatment of many diseases including cancer treatment. Conventional ways of drug administration are often characterized by a limited effectiveness, poor biodistribution and lack of selectivity. Fortunately, this limitation could be overcome by using drug nanocarriers. In this context, metal-organic frameworks (MOFs) - porous coordination polymers – seem to be very promising. MOFs comprise two building components – metal ions (or clusters) and polydentate organic ligands. They are known as materials featuring a high internal surface area, which can be used to load various molecules including drugs. In our research we focus on the delivery of arsenic drugs. Arsenic compounds such as arsenic trioxide have been shown as promising drugs in cancer treatment but due their high intrinsic toxicity, their delivery in therapeutic concentrations is challenging. Here nanomedicine and nanoparticles as drug carriers show great potential. Moreover, by combining MOF nanoparticles with agents suitable for magnetic resonance imaging such as superparamagnetic Fe3O4 nanoparticles, we could prepare theranostics, i.e. materials suitable not only for drug delivery but also for diagnosis. Such materials are expected to play a significant role in the dawning era of personalized nanomedicine.

Online Seminar #6: Dr. Viktor Hlukhyy

Dr. Viktor Hlukhyy (Technische Universität München)
May 25, 2021
6:00-7:30pm (Berlin time)

"Fe-, Co- and Ni- based polar intermetallic compounds: synthesis, structural peculiarities and properties"
Given the fact that the chemical composition and crystal structure of a compound define its properties, a thorough understanding of the factors that allow for the realization of a certain combination of elements is an essential point when designing new applicable materials. In the case of intermetallic compounds, however, the composition-structure-property relationships are often poorly understood. Complex structural chemistry of such polar intermetallics is caused by an interplay between covalent, metallic, and ionic interactions. The discovery of high-temperature superconductivity in iron-pnictides has sparked enormous interest in intermetallic compounds containing square-planar lattice arrangement of transition metal atoms, particularly in ThCr2Si2-type representatives. It is known that the superconducting properties are very sensitive to the structural parameters of d-metal layers, and as such the structural flexibility for chemical substitution in ThCr2Si2-type materials makes this family of intermetallic compounds interesting candidates for studying the structure-property relationship. In this talk, the synthesis, structural features, and magnetic properties of new polar intermetallic compounds based on iron, cobalt, and nickel, with square-planar layers and other 2D-, 1D- and 3D- arrangements of transition metal atoms will be discussed.

Online Seminar #5: Dr. Bertold Rasche

Dr. Bertold Rasche (Universität Köln)
April 27, 2021
6:00-7:30pm (Berlin time)

“Can Electrochemistry Help to Understand Superconductivity? – In-situ electrochemical X-ray diffraction of β-Fe1+xSe”
Systematic investigations of phase systems and transitions are the foundation of understanding complex physical phenomena such as superconductivity. One example in which the lack of such a systematic knowledge has led to contradictory results is β-Fe1+xSe. The superconductivity of this “simple” two-dimensional, layered structure has been reported to be heavily dependent on the composition and closely related structural transitions, defects and various superstructures with overall inconsistent results. The difficulties arise from the narrow phase width of β-Fe1+xSe (0.01 < x < 0.04), a small deviation from the 1:1 ratio and its manifold of neighbouring phases. We report the precise post-synthetic control of the composition of β-Fe1+xSe by electrochemistry with simultaneous tracking of the concomitant structural changes via in-situ synchrotron X-ray diffraction. Via an externally applied potential, electrochemistry allows us to confirm the phase width of 0.01 < x < 0.04. We identify the superconducting state below 8 K, which in contrast to earlier reports is independent of the composition. However, in a second set of in situ X-ray diffraction experiments, we demonstrate that β-Fe1+xSe forms a new phase in the presence of oxygen above a 100 °C, which has the same anti-PbO type structure but is not superconducting down to 1.8 K. This electrochemical approach takes experiments for two-dimensional materials beyond intercalation reactions, and exploits the exquisite control provided by electrochemistry.

Online Seminar #4: Janine George

Dr. Janine George (Université catholique de Louvain)
April 13, 2021
6:00-7:30pm (Berlin time)

„Data-driven materials discovery and chemical understanding“
Developments in density functional theory (DFT) calculations, their automation and easy access to materials data have enabled ab initio high-throughput searches for new materials for numerous applications. These studies open up exciting opportunities to find new materials in a much faster way than based on experimental work alone. However, performing density functional theory calculations for several thousand materials can still be very time consuming. The use of, for example, faster chemical heuristics and machine-learned interatomic potentials would allow to consider a much larger number of candidate materials. In addition to DFT based high-throughput searches, the seminar will discuss two possible ways to accelerate high-throughput searches. Using data analysis on the structures and coordination environments of 5000 oxides, we were able to investigate a chemical heuristic – the famous Pauling rules – regarding its usefulness for the fast prediction of stable materials. We have also investigated how machine-learned interatomic potentials can be used to accelerate the prediction of (dynamically) stable materials. The use of these potentials makes vibrational properties accessible in a much faster way than based on DFT. Our results based on a newly developed potential for silicon allotropes showed excellent agreement with DFT reference data (agreement of the frequencies within 0.1-0.2 THz). In addition, we have successfully used high-throughput calculations in the search for new candidate materials for spintronic applications and ferroelectrics.

Online Seminar #3: Sebastian Henke

Jun.-Prof. Dr. Sebastian Henke (TU Dortmund)
March 30, 2021
6:00-7:30pm (Berlin time)

„Stimuli-Responsiveness, Melting and Glass Formation of Metal-Organic Frameworks “
Metal-organic frameworks (MOFs) are an emerging family of porous solid-state materials exhibiting huge potential for various technological applications (gas storage/separation, catalysis, drug delivery, sensing, etc.). These compounds are composed of inorganic building units (typically d-block metal ions, metal-(oxo/hydroxo)-clusters) which are interconnected by multidentate organic linkers to generate two- or three-dimensional extended networks, exhibiting huge internal surface areas and pore volumes. In this talk, I present our recent efforts in different areas of MOF chemistry. Firstly, I introduce flexible MOFs, which undergo dramatic structural changes as a function of guest molecule adsorption/desorption, temperature or mechanical pressure. By chemical modification or exchange of the frameworks’ building units, the structural response of the MOF can be tunes systematically. Secondly, I demonstrate the preparation of liquid MOFs and their corresponding glasses. MOF glasses represent a new class of glassy materials and own intrinsic porosity, similar to their crystalline parent compounds. We revealed that MOF glasses are able to adsorb even relatively large hydrocarbon gas molecules, thus enabling kinetic gas separation (i.e. the separation of propylene from propane). Finally, I present a new concept for the design of porous framework materials that can be processed (i.e. drop casted, crystallized, etc.) from aqueous solution. Our materials design strategy is based on amphiphilic organic building blocks which reversibly assemble/disassemble to micellar porous frameworks, mediated by coordination to alkali ions in aqueous solution.

Online Seminar #2: Oliver Clemens

Prof. Dr. Oliver Clemens (Universität Stuttgart)
March 23, 2021
6:00-7:30pm (Berlin time)

“Anion Chemistry of Energy Materials – Batteries, Tunable Properties, and Electrocatalysts”
Without doubt, topochemical reactions play an important role for our current batteries, e.g., within oxide-based cathode materials or carbon-based anode materials for lithium-ion batteries. However, topochemistry of oxide materials is by no means restricted to small cations, and perovskite as well as perovskite-related materials possess a vivid insertion chemistry for anions, making them interesting compounds for a broad range applications related to their multitude of functional properties, among them magnetism and superconductivity. In this talk, the use of topochemical reactions with anions to develop and understand new energy materials with tailored and tunable properties will be highlighted. These reactions cover the preparation of oxyfluorides and oxyhydroxides for fluoride-ion batteries and electrocatalytic (SOFC and PCFC) applications. Special focus will be set on using topochemistry for the reversible on/off-switching of material properties. Last but not least, the impact of anion and vacancy ordering on the intrinsic properties will be given, with a special focus on barium ferrates and cobaltates with perovskite-related structure, for which novel compounds could be prepared and structurally characterized.

Online Seminar #1: Harun Tüysüz

PD Dr. Harun Tüysüz (MPI für Kohlenforschung)
March 2, 2021
6:00-7:30pm (Berlin time)

“Tailor-made Nanostructured Materials for Energy Conversion Applications”
My particular research interest is the design of well-defined nanostructured materials and studying their structure-activity relationships for sustainable energy-related catalytic applications. The focus of the first part of the lecture will be design and development of Co, Ni and Fe based electrocatalysts for oxygen evaluation reactions. This will be followed by the presentation of solid-state inorganic halide perovskites and their implementation as functional photocatalysts for prototype reactions.

zuletzt geändert am: 18.06.2021 06:40 Uhr von M.Fries