2026 marks the 100th birthday of the concept of point defects in crystals!
It may not be obvious on its’ face, but none of the modern cutting-edge technologies in PV energy generation, batteries, “electrification of everything”, “quantum” or “AI” that dominate discourse today would be possible without 100 years and millions of person-hours of work on point defects!
What’s this all about?
This is a fun scholarly effort for me, driven originally simply by my unquenchable curiosity and realized through, dogged perseverance in Googling, fundamental appreciation that we can learn from people in the past (thanks to my Dad for kindling that appreciation), and enthusiasm and effort from friends and colleagues. This whole effort started after I attended the 2023 International Conference on Defects in Semiconductors (ICDS) in Rehobeth Beach, NJ (organized by Jack and Anderson) and, after unfortunately missing Chris van de Walle’s talk on historical developments, was wondering “Who first came up with the idea of point defects?” I started asking around (thanks Matt, Mike, and Beal!) and following citation trails but finally found my way to some papers laying out a history of point defects. They all pointed back to names you’ll know (Frenkel and Schottky) and some you might not but should (Wagner). Of course, humans have appreciated things like color centers in crystals for much longer, but I’m defining the start here as when somebody first codified the idea that whenever atoms are missing, extra, or misplaced in a crystal, that atomic-scale structural disorder produces changes in properties. Turns out the first things they were trying to figure out were how ions carry current in crystals – so they skipped the simple stuff like “Why do crystal insulators have color sometimes?” and went straight to drift-diffusion! This is the fun part, getting to go back to the beginning in order to fully understand where we are today, and then build towards the future from there. Join in!
100 Years of Point Defects Symposium at MRS Fall 2026:
In early December 2025, we were approved to hold a birthday party for point defects at MRS Fall 2026 in Boston (hmm, what will the cake be?). More to come but huge thanks in advance to co-organizers Jack Lyons (US Naval Research Lab), Izabela Szlufarska (U Wisconson), and Jennifer Rupp (TU Munich). Check back in next months for updates.
MRS Bulletin May 2026 Issue:
Co-Guest-Editors Mike Scarpulla (UUtah), Jack Lyons (Naval Research Lab), Elif Ertekin (U Illinois), and Filip Tuomisto (U Helsinki) are organizing the May 2026 issue of MRS Bulletin Crystalline Point Defects: Past, Present, and Future at 100 Years. The topic is too big to truly do it justice in a handful of articles (and we apologize up front that we will inevitably leave some topics and important contributions out), but we have nonetheless assembled a great group of coauthors to give snapshot articles of the current frontiers of research in point defects.
Frontiers of Materials Research in Point Defects (the guest editors)
Frontiers of Computation for Defects in Semiconductors and Insulators (Mark E. Turiansky, John L. Lyons, Darshana Wickramaratne, Joel B. Varley, and Anderson Janotti)
Frontiers of Defect Description in Complex Solid-State Ionic Materials (Vanessa Woo, Channyung Lee, Bilge Yildiz, Elif Ertekin , and Nicola H. Perry)
Spectroscopy of point defects in semiconductors (Matthew D. McCluskey, Michael A. Reshchikov, Hemant Ghadi, Joe F. McGlone, Steven A. Ringel, Patrick M. Lenahan, Kai-Mei Fu, and Filip Tuomisto)
Point Defect Kinetics in Semiconductors: Experimental Insights, Modeling Approaches, and Applications (Leopoldo Diaz, Arthur H. Edwards, Daniel M. Fleetwood, Harold P. Hjalmarson, Kai Nordlund, Ronald Schrimpf, Peter A. Schultz, Edmund G. Seebauer, William R. Wampler, and William J. Weber)
Machine Learning Techniques in Defect Theory (Arun Kumar Mannodi Kanakkithodi, Maria Chan, Prashun Gorai, and Sean R. Kavenaugh)
Point defects for Quantum Information (Geoffroy Hautier, et al)
Other Ways to Celebrate:
Study and appreciate point defects and their impacts on science and technology. Imagine all of the aggregated human effort over 100 years that has given us everything from batteries in electric vehicles, to semiconductor chips, to LEDs and solid state lasers, … Also, nature figured this out millennia ago and gave us beautiful gemstones colored by these rare but critical flaws!
Start Other Events Within Your Professional Organizations and Conferences!
If you care about point defects, start a similar effort in your professional society – ACS, ACERS, APS, and all the international Chemistry, Materials, Semiconductor, Crystallography, and Physics societies.
Read (and help translate, if you can) the original papers from German to your language!
Many of the landmark papers are pretty hard to find, but after 2 years of persistence (thank you The Internet Archive!), I’m pleased to post these (out of copyright) original papers from 100 years ago.
HELP WANTED! Finding these old citations is a bit challenging and LLMs can only do so well on translating unique documents like these. If you’ve got a dusty old book on a shelf please scan it for the world (of course respect copyrights). If you’re a publisher, please consider sharing such foundational works – really cultural artifacts – with humanity rather than keeping them in obscurity. Please consider scanning these things, releasing copyrights into public domain, and commissioning or allowing translations. If you are bilingual in German and {English, …. , any other language} please help translate these historical documents to make them available to all! Find other key papers and rescue them from obscurity.
https://immersivetranslate.com/ – I’m finding this to be a great tool to see side-by side translations. When I started trying to read Frenkel just 2 years ago, Google translate was the best option (and it created a mess of text overlaid on the original so you couldn’t read either one). How fast things are moving with AI (powered by CdTe or Si solar cells, with Li ion back-up batteries, on CPUs and GPUs made of doped silicon, powered by GaN power circuits, in buildings with InGaN LED lighting, and the info sent over fiber internet by InGaAs lasers, …).
Works Having Coverage of History of Crystal Defects
Pearson & Brattain – History of Semiconductor Research – Proceedings of the IRE (1956)
Pick – Color centers in alkali halides (1958)
Wagner – Point Defects and Their Interaction (1977)
Szymborski – The Physics of Imperfect Crystals-A Social History (1984)
Nowick – The Golden Age of Crystal Defects (1996)
Martin – Life and achievements of Carl Wagner, 100th birthday (2002)
Knauth & Tuller – Solid‐State Ionics: Roots, Status, and Future Prospects – Knauth (2002)
Funke – Solid State Ionics: from Michael Faraday to green energy—the European dimension (2013)
Landmark Papers in Point Defects
Joffe (Ioffe) (1923)- This is apparently what started Frenkel thinking about how ions could move through crystals. Joffe showed that bias caused a current to flow vs time through some dielectrics. The basic phenomena are akin to charging a parallel plate capacitor through a really big resistor (now we understand that the resistance is the low mobility of mobile ions, and they were being depleted from one side and piled up on the other).
Frenkel (1926) – most commonly cited as THE first time anyone imagined (or at least wrote down their imaginings) how pairs of point defects could form in a crystal as a result of rare, high-amplitude lattice vibrations. It seems this was a one-off masterwork – like Athena emerging fully-formed from Zeus’s skull.
Carl Wagner and Walter Schottky (1930-1935) – These two wrote a series of papers in the early 1930’s. All intros on point defects in physical chemistry, materials science, etc cover Frenkel and Schottky disorder (why isn’t it called Wagner-Schottky disorder? Wagner was first author..).
Wagner and Schottky (1930) – On the theory of mixed phases (or something close to this). They were essentially trying to figure out how “line” compounds in phase diagrams accommodate off-stoichiometry.
Mystery paper – in 1972 Kroger cites a paper by Wagner apparently part of a “Festband” for Prof. Bodenstein published in Z. Chem Phys. I have not been able to track this down yet… maybe the citation is muddled? Please notify me if you can scan or find a PDF of: C. Wagner, Z. Phys. Chem., Bodenstein Festband (1931), p. 177 (is this a book? A special issue?) Citation found in Kroger’s Defect Thermodynamics – Historical in Defects and Transport in Oxides, Battelle, (1973).
Schottky 1935 – Many citation trails give this one as it seems Wagner and Schottky fully developed their ideas within 5 years and Schottky wrote it up.
Schottky, Ulich and Wagner – Thermodynamik, Springer Berlin – They put their new theories into the textbook they were writing too. It would be awesome to get this section scanned, translated, and shared.
Jost The energies of disorder in ionic crystals (1938) – not sure if this is a classic but it is early. 39 citations in 1938 was probably a big number.
Seitz (1946) – Color Centers in Alkalai Halide Crystals Rev Mod. Phys. (1946)
Hebb – Electrical Conductivity of Silver Sulfide | The Journal of Chemical Physics (1952)
Kroger and Vink – Relations between the concentrations of imperfections in solids (1958)
Useful and Interesting References
Bridges – The spectroscopy of crystal defects: a compendium of defect nomenclature (1990)