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Johannes Margraf

@jtmargraf.bsky.social
179 followers 250 following 34 posts

All day I dream about science! Computational chemistry, machine learning, electronic structure. margraf.uni-bayreuth.de

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Johannes Margraf @jtmargraf.bsky.social · 18/09/2026
Hydrogen orbitals!
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Johannes Margraf @jtmargraf.bsky.social · 22/08/2026
Just a rainy day in the soccer stadium 😉
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Johannes Margraf @jtmargraf.bsky.social · 21/08/2026
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Johannes Margraf @jtmargraf.bsky.social · 30/07/2026
static.klipy.com
Asterix Drinks Magic Potion
ALT: Asterix Drinks Magic Potion
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Johannes Margraf @jtmargraf.bsky.social · 26/07/2026
A great loss!
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Reposted by Johannes Margraf
Karel "CaCO3" Berka @krapnik.bsky.social · 26/07/2026
Sad news to #CompChem Pavel Jungwirth passed away… www.uochb.cz/en/news/811/...
uochb.cz
Pavel Jungwirth, a leading figure in the world of chemistry, has died
The Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences is deeply saddened to announce that on Thursday 23 July 2026, our outstanding colleague, teacher, mentor and…
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Johannes Margraf @jtmargraf.bsky.social · 19/07/2026
Murmeltier
A picture of a Marmite in the mountains
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Johannes Margraf @jtmargraf.bsky.social · 18/07/2026
A giant of theoretical chemistry!
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Johannes Margraf @jtmargraf.bsky.social · 11/06/2026
Welcome to the dark side!
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Johannes Margraf @jtmargraf.bsky.social · 13/05/2026
Yes! And the "solutions" (a new virtual environment or docker for every script) are often worse than the problem!
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Johannes Margraf @jtmargraf.bsky.social · 09/05/2026
Thanks for sharing! This is a central questions for MLIPs. Now that we figured out how to fit energies and forces accurately, how can we tell if the models reproduce DFT observables in downstream tasks. We've looked at this for crystal structure prediction doi.org/10.1002/aidi...
doi.org
Universally Accurate or Specifically Inadequate? Stress‐Testing General Purpose Machine Learning Interatomic Potentials
We investigate MACE-MP-0 and M3GNet, two general-purpose machine learning potentials, in materials discovery and find that both generally yield reliable predictions. At the same time, both potentials....
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Johannes Margraf @jtmargraf.bsky.social · 22/04/2026
"We thank the reviewer for their insightful comment."
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Johannes Margraf @jtmargraf.bsky.social · 07/04/2026
We developed a new in-browser data analysis tool for educational purposes called tinyplot. You can try it out here: margrafgroup.github.io/tinyplot/ It uses pyscript, so the first time you use it, there's some overhead of importing the underlying libraries. I'd be really interested in feedback!
margrafgroup.github.io
TinyPlot
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Johannes Margraf @jtmargraf.bsky.social · 31/03/2026
A desert
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Johannes Margraf @jtmargraf.bsky.social · 18/03/2026
As a rule of thumb: where are the articles you cited published? That's what I would aim for.
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Reposted by Johannes Margraf
Avogadro Project @avogadro.cc · 14/03/2026
Avogadro 2.0 drops April 1st — and no, that's not a joke! 🧪⚗️ Now's the perfect time to help improve translations before release. Every language matters for chemistry worldwide. #opensource #openscience hosted.weblate.org/engage/avoga...
hosted.weblate.org
Making sure you're not a bot!
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Johannes Margraf @jtmargraf.bsky.social · 13/03/2026
Thanks, such a cool conference!
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Reposted by Johannes Margraf
Raunak Farhaz @raunakfarhaz.bsky.social · 08/03/2026
A very good read by @philipcball.bsky.social
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Johannes Margraf @jtmargraf.bsky.social · 06/03/2026
Blue
Blue abstract picture
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Johannes Margraf @jtmargraf.bsky.social · 02/03/2026
It consistently and confidently suggested wrong or outdated syntax, to the point that it was slowing the process down until I abandoned it. I found the difference between the performance for html/js and pyscript really interesting. Not surprising as such, but unexpected in magnitude.
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Johannes Margraf @jtmargraf.bsky.social · 02/03/2026
But then, for some numerical stuff, I wanted to use pyscript. This is a need library that lets you run python in the browser via web assembly. It's fairly new, and the API for interacting between python and js has changed pretty significantly between versions. Here the llm was completely useless 3/n
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Johannes Margraf @jtmargraf.bsky.social · 02/03/2026
The experience was interesting but pretty mixed. The thing that worked really well was coding up the front-end of a web app in html and javascript. This ran out of the box from a pretty minimal prompt, and the design choices of the llm were quite nice. 2/n
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Johannes Margraf @jtmargraf.bsky.social · 02/03/2026
I did my first bigger coding project with an llm today (copilot w gpt-5). Usually, for the things I do for research, writing the code is not the time limiting factor, and I do it in python, which I know well. This was for a teaching project involving javascript and html, which I barely know. 1/n
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Reposted by Johannes Margraf
Geoff Hutchison @geoffhutchison.net · 26/02/2026
I share the sad news that Prof. David H. Waldeck passed away after a battle with cancer. Dave was an extraordinarily creative scientist, a devoted educator, and to all of us a friend, mentor, and leader. He will be deeply missed #chemsky #chemchat
Photograph of David Waldeck - in the background is the University of Pittsburgh's Cathedral of Learning
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Reposted by Johannes Margraf
Stefan Bon 🏳️‍🌈🎸🐕 @bonlab.info · 26/02/2026
We are looking for two talented people to join us at the Department of Chemistry at the University of Warwick as assistant professors. Permanent positions. 🧪🍎🥽 warwick-careers.tal.net/vx/appcentre...
warwick-careers.tal.net
Assistant Professor in Chemistry x2 (111367-0226) - University of Warwick
Title: Assistant Professor in Chemistry x2 (111367-0226). Application Deadline: . Position Type: Permanent
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Reposted by Johannes Margraf
Volker Blum @aimsduke.bsky.social · 25/02/2026
Here is Rayan Chakraborty's masterpiece doi.org/10.1021/jacs... showing some new 3D halide perovskites. That's very rare! Again, thanks to Department of Energy, NSF and Duke Climate Initiative. Oh, and a modest 3672 atom DFT simulation probing the local order (along with many other simulations)!
doi.org
Local Symmetry Breaking in 3D Hybrid Perovskites with 3-Hydroxyazetidinium
Two-dimensional (2D) hybrid perovskite semiconductors with nonprimary ammonium cations (NPACs) have recently attracted interest for spin-optoelectronics owing to the symmetry-breaking distortions in their crystal structures. However, implementing this design strategy in three-dimensional (3D) analogs remains largely unexplored, primarily due to stricter restrictions on cation size. Here, we introduce a family of 3D hybrid perovskites (3DHPs), ASnX3, where A = 3-hydroxyazetidinium (AzOH; +NH2(CH2)2CHOH) and X = Cl, Br, and I. The choice of a bulky NPAC, coupled with the incorporation of a polar group (−OH), targets broken symmetry within the 3D frameworks. While single-crystal X-ray diffraction analysis reveals spatially averaged centrosymmetric cubic (i.e., Pm-3m space group) unit cells, with the largest lattice parameters among existing ASnX3 analogs, first-principles molecular dynamics and electronic structure calculations indicate that the relatively fixed dipoles of AzOH within the SnX6-derived framework introduce local inversion asymmetry and spin polarization. By incorporating a polar cation with limited mobility into the 3D perovskite framework, (AzOH)SnX3 unlocks potential for spin-optoelectronics, photovoltaics, ferroelectrics, and nonlinear optics.
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Johannes Margraf @jtmargraf.bsky.social · 25/02/2026
Really cool stuff!
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Johannes Margraf @jtmargraf.bsky.social · 25/02/2026
Blame it on the character limit. Wagner is too epic for 300 characters ⚔️
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Johannes Margraf @jtmargraf.bsky.social · 25/02/2026
📢 We're hiring a PhD student in ML for Materials Chemistry at Uni Bayreuth! Apply if you're into atomistic simulations and the intersections between physics, chemistry and ML. We offer a great environment in one of the nicest towns in Germany. Apply here: bit.ly/4aPBgE9. #compchem #chemsky
uni-bayreuth.de
Job advertisement of the University of Bayreuth  - Chair of Physical Chemistry V: Theory and Machine Learning
Fixed-Term Research Associate (m/f/d, E13 TV-L, 67%) in the field of Machine Learning for Materials Chemistry
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Johannes Margraf @jtmargraf.bsky.social · 25/02/2026
Bubbles 2
Abstract blue and yellow picture with some bubbles on the right side.
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Johannes Margraf @jtmargraf.bsky.social · 24/02/2026
Yes, I'm pretty happy with the feedback so far. Lots of people I remember from Twitter, some I know in person.
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Johannes Margraf @jtmargraf.bsky.social · 23/02/2026
Not even close for me (just JPC).
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Johannes Margraf @jtmargraf.bsky.social · 22/02/2026
Thanks, nice example! With the hype around generative ML models, the number of candidates for 'designed' materials of course increased substantially in recent years. My feeling is that the number of candidates is not necessarily the limiting factor, though.
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Johannes Margraf @jtmargraf.bsky.social · 22/02/2026
That mix of disappointment and relief when weekend plans get canceled at the last minute. I'm sure there's a German word for that. (I'm German. There isn't.)
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Johannes Margraf @jtmargraf.bsky.social · 22/02/2026
Funnily enough, these are certainly not the most sophisticated calculations or ML models we have used, but the key was to be in exchange with experimentalists from an early stage in the project, to ensure that we are predicting things they actually can and want to make.
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Johannes Margraf @jtmargraf.bsky.social · 22/02/2026
I would say our own clearest examples of this is this work with @jabla.bsky.social and @lotschgroup.bsky.social: pubs.acs.org/doi/full/10.... and this one with Stefan Hecht: pubs.rsc.org/en/content/a...
pubs.acs.org
Predict before You Precipitate: Learning Templating Effects in Hybrid Antimony and Bismuth Halides
Hybrid organic–inorganic (HOI) antimony and bismuth halides exhibit diverse structural features and have been studied intensely for their promising electronic and optical properties. There are well-explored structure–property relations for these materials. However, a thorough understanding of the synthesis routes and templating effects is lacking, turning their targeted synthesis into an open challenge. In this study, we assemble a literature data set of established HOI material candidates and train an explainable machine learning classification model to explore the templating effects in more detail. With a classification accuracy upward of 70%, our model is effective in predicting HOI structure types based on the reactants and points out several structural and electrostatic design features for the organic cation that influence the inorganic substructure most strongly. We further demonstrate the validity of our classifier on 9 newly synthesized members of this materials class and propose incremental learning routes to expand the model in future research.
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Johannes Margraf @jtmargraf.bsky.social · 22/02/2026
Thanks, this is a nice example. I get the impression, that this is still pretty rare. Not because the methods are not accurate enough, but because the connection between computational and experimental groups is missing.
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Johannes Margraf @jtmargraf.bsky.social · 21/02/2026
What's your favorite example of the computational discovery/prediction of a new material? #chemsky
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Johannes Margraf @jtmargraf.bsky.social · 21/02/2026
Bubbles
Abstract picture that looks like bubbles are  leaving a coarse cube downwards.
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Reposted by Johannes Margraf
Lars Fischer @fischblog.bsky.social · 17/02/2026
Hi #chemsky, I have been asked to come up with chemistry ideas for a new teaching format at german schools that focuses on democracy. What's lacking are ideas how to use chemistry in this context. So what could be the chemistry of democracy and how do you present it in a school lesson?
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Johannes Margraf @jtmargraf.bsky.social · 16/02/2026
Hello bluesky, I'm a theoretical chemist at University of Bayreuth. My group works on atomistic modeling of energy materials with electronic structure methods and ML. I'm hoping to connect to other #compchem and #materials folks!
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