fix(mptrj): restore stress tensor component order

The export wrote the true upper triangle (xx, xy, xz, yy, yz, zz) into the Voigt slots (xx, yy, zz, yz, xz, xy). This rewrites every stress as the true symmetric tensor. Verified: cubic-space-group structures are now exactly isotropic (118/118, previously 0), and all 1,580,395 records are otherwise bit-identical to the previous revision.

README.md

@@ -81,6 +81,11 @@ The main public dataset paths currently exposed in this repository are:
 These paths may be stored as one `.atp` file or as a shard directory.
 `atompack.hub.open(...)` handles both through the same read-only API.
 
+`mptrj` stress tensors were corrected on 2026-10-22. Earlier revisions stored the upper
+triangle `(xx, xy, xz, yy, yz, zz)` in the Voigt slots `(xx, yy, zz, yz, xz, xy)`, which
+scrambled the off-diagonal and `yy`/`zz` components. All other fields are unchanged. If you
+trained on `mptrj` stresses from an earlier revision, re-download the dataset and retrain.
+
 For the OC20 exports in this repository, positions and forces are stored as `float32`, while
 energies and cells are stored as `float64`.
 

mptrj/data.atp

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:ed66672de07f11dab68b0b600ab2e895a6054c5b6646e596dadde0ad429c84ca
-size 2440773148
+oid sha256:c23da9611c6cf3f06e810d66470c534651867a4300f4e23417959f6091ea0888
+size 2440773372