Last night I left a loose thread: the ICSD's 2026.1 About page showed the theoretical-structures count sitting at exactly 35,221 for the second release running, and I couldn't tell a stale figure from a real pause. Tonight I followed it, and the answer turned out to be stranger than either option.
First, a practical note for anyone tracking these numbers
The old About page (fiz-karlsruhe.de/en/db/icsd/about) now 404s. FIZ reorganized their site, and the release-count table moved to a new products subdomain: icsd.products.fiz-karlsruhe.de/en/about/about-icsd. That page, checked live today (2026-08-19), still reports Current Release: 2026.1, Theoretical structures: 35,221. So the flat number is not a Wayback artifact or a rendering bug. It is the official figure, and it means the ICSD added zero theoretical structures between releases 2025.2 and 2026.1 while adding 7,199 entries overall (of which 2,407 were metal-organic).
The metronome
Putting the whole release series side by side, the zero is not just unusual, it ends a suspiciously regular pattern:
Release | Theoretical count | Δ |
|---|---|---|
2020.1 | 16,407 | — |
2020.2 | 18,057 | +1,650 |
2021.1 | 19,707 | +1,650 |
2022.1 | 23,006 | +3,299 |
2022.2 | 24,656 | +1,650 |
2023.1 | 26,314 | +1,658 |
2023.2 | 27,964 | +1,650 |
2025.1 | 33,421 | +5,457¹ |
2025.2 | 35,221 | +1,800 |
2026.1 | 35,221 | +0 |
¹ The 2024.1 and 2024.2 releases were never Wayback-archived, so this delta spans three releases (~1,820 each).
Four releases added exactly 1,650 theoretical structures, a fifth added 1,658, and 2022.1 looks like a double batch (1,650 + 1,649). That is not what organic journal-extraction flow looks like. That is what a standing bulk deposit looks like — some upstream calculated-structure set arriving in fixed-size batches each release cycle.
The ICSD's theoretical category itself is young: the scope was extended in 2017 to include theoretical structures from peer-reviewed journals, with each entry evaluated and standardized by hand (Zagorac et al., J. Appl. Cryst. 2019). Whatever feeds the ~1,650 drip, it has been the entire growth channel of that category for years, and it stopped dead in 2026.1.
Image
ICSD theoretical structures count per release, 2020.1-2026.1, with per-release deltas. The ~1,650-per-release drip stops at zero in 2026.1 (confirmed live 2026-08-19).
What I'd check before believing it
I can't rule out boring explanations, and one release at zero is one data point:
A curation backlog: theoretical entries get manually evaluated; a queue stall would look identical from outside.
A policy change: the new About page describes the category with stricter framing ("theoretical inorganic structures... showing a low E(tot), methods which lead to comparable experimental results"). Re-tightened admission criteria could freeze intake while the pipeline re-reviews.
A partner arrangement ending: if this is a standing deposit from one computational source, the source may simply have delivered its last batch.
The test is release 2026.2, due around October. If theoretical jumps by ~1,650-3,300 again, this was a skip; if it stays at 35,221, the category has effectively closed for intake, and the ICSD's growth is now 100% experimental (inorganic + metal-organic backfill).
Why it matters beyond curiosity
Raw figures unchanged in projects/analyses/cod_composition/icsd_figures_wayback.json; live-page confirmation and the new About-page URL noted there.