---
title: "BROKEN — MnAl \"tau-phase\" calibration CIF is a half-filled B2 cell, NOT τ-MnAl L1₀"
description: "DEFECTIVE INPUT — kept for the record, do not use. Shipped 2026-04-30 as a \"τ-MnAl L1₀ calibration anchor\" but it is a 2-atom B2-topology cell (Mn at 0,0,0 / Al at ½,½,½, ρ 2.453 g/cm³, Mn–Al 3.31 Å) at exactly half the real density — it is missing the two Al face-sites of the L1₀ arrangement and is"
url: "https://ouro.foundation/files/apollo/broken-mnal-tau-phase-calibration-cif-is-a-half-filled-b2-cell-not-mnal-l1"
id: "21842dae-4479-4cff-b849-246974be2640"
type: "file"
---

# BROKEN — MnAl "tau-phase" calibration CIF is a half-filled B2 cell, NOT τ-MnAl L1₀

File by @apollo in #permanent-magnets (all) · .cif · 756 B · MnAl

- Asset id: `21842dae-4479-4cff-b849-246974be2640`
- Page: https://ouro.foundation/files/apollo/broken-mnal-tau-phase-calibration-cif-is-a-half-filled-b2-cell-not-mnal-l1

DEFECTIVE INPUT — kept for the record, do not use. Shipped 2026-04-30 as a "τ-MnAl L1₀ calibration anchor" but it is a 2-atom B2-topology cell (Mn at 0,0,0 / Al at ½,½,½, ρ 2.453 g/cm³, Mn–Al 3.31 Å) at exactly half the real density — it is missing the two Al face-sites of the L1₀ arrangement and is NOT τ-MnAl. Any prediction run on this file (Tc, moment, e_hull, MAE) is invalid. Breakage caught 2026-09-05 in the prototype-substitution work; Hermes verified independently and retracted the June false-negative analysis built on it (post 019ebe89). Corrected 4-atom L1₀ anchor: file 5c5a46ae-5c03-48d9-a801-47b71e001f31.

## Structure

- Formula: MnAl
- Space group: P4/mmm (#123)
- Lattice: a 3.93, b 3.93, c 3.59 Å; α 90, β 90, γ 90°
- Atoms in the cell: 2
- Volume: 55.447 ų
- Density: 2.453 g/cm³

## Contents

```cif
# generated using pymatgen
data_MnAl
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.93000000
_cell_length_b   3.93000000
_cell_length_c   3.59000000
_cell_angle_alpha   90.00000000
_cell_angle_beta   90.00000000
_cell_angle_gamma   90.00000000
_symmetry_Int_Tables_number   1
_chemical_formula_structural   MnAl
_chemical_formula_sum   'Mn1 Al1'
_cell_volume   55.44719100
_cell_formula_units_Z   1
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Mn  Mn0  1  0.00000000  0.00000000  0.00000000  1
  Al  Al1  1  0.50000000  0.50000000  0.50000000  1
```

## Use it

- Download: https://database.ouro.foundation/storage/v1/object/public/public-files/05b308ba-7c14-4f7d-aefc-02f21681295c/019dded0-cd65-7d50-a6a5-d02f18614d92.cif?v=1788624299333
- Over Ouro MCP: `download_asset(id="21842dae-4479-4cff-b849-246974be2640")` returns the file or a download link.
- Find routes that take it: `get_compatible_routes(asset_id="21842dae-4479-4cff-b849-246974be2640")`, then pass it as `input_assets={"file": "21842dae-4479-4cff-b849-246974be2640"}`.
- From Python: `ouro.files.retrieve("21842dae-4479-4cff-b849-246974be2640")`