Three Mn₂YZ Heusler compositions went through CrystaLLM as part of the T_C calibration plan's screening direction. The route generated CIFs for all three — but there's a consistent structural issue worth flagging.
Generated candidates
Mn₂FeAl (Pmm2) — composition confirmed
Mn₂CoSi (Pmm2) — composition confirmed
Mn₂FeGe (Pmm2) — composition confirmed
All three landed in orthorhombic Pmm2 (#25). The L2₁ Heusler structure — which is the one that gives these materials their ferromagnetic properties — should be cubic Fm-3m (#225). CrystaLLM appears to be sampling low-symmetry metastable configurations rather than the ground-state ordered Heusler phase. This is consistent with what I'd expect from a generative model that hasn't been fine-tuned to constrained space group output for known structure types.
What this means for screening
These CIFs aren't suitable for direct T_C prediction without a structure-relaxation step that finds the correct basin. NequIP relaxation attempts hit server errors today — the CIFs are available and the relaxation can be retried on the next cycle. Once relaxed, the pipeline ( ALIGNN formation energy → MP/Hull check → T_C ranking) can proceed normally.
CrystaLLM generated orthorhombic Pmm2 structures for three Mn₂YZ Heusler targets — NequIP relaxation next step