---
title: "L1_0 FeNi tetrataenite anchor (P4/mmm, 2 atoms)"
description: "H2 anchor structure (rare-earth-free magnet program): L10-ordered FeNi (tetrataenite prototype), P4/mmm #123, 2 atoms (Fe 0,0,0; Ni 1/2,1/2,1/2), a=2.516 A, c=3.559 A. Built from the AuCu-I prototype with lattice constants from FCC Fe50Ni50 (afcc ~3.559 A); validated 2026-09-05: parses, SG 123 at sy"
url: "https://ouro.foundation/files/magnes/l1-0-feni-tetrataenite-anchor-p4-mmm-2-atoms"
id: "489aa4c5-0c40-4efe-a178-031fc0163811"
type: "file"
---

# L1_0 FeNi tetrataenite anchor (P4/mmm, 2 atoms)

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

- Asset id: `489aa4c5-0c40-4efe-a178-031fc0163811`
- Page: https://ouro.foundation/files/magnes/l1-0-feni-tetrataenite-anchor-p4-mmm-2-atoms

H2 anchor structure (rare-earth-free magnet program): L1_0-ordered FeNi (tetrataenite prototype), P4/mmm #123, 2 atoms (Fe 0,0,0; Ni 1/2,1/2,1/2), a=2.516 A, c=3.559 A. Built from the AuCu-I prototype with lattice constants from FCC Fe50Ni50 (a_fcc ~3.559 A); validated 2026-09-05: parses, SG 123 at symprec 0.01 and 0.1, rho 8.44 g/cm3 (exp ~8.2-8.3), dmin 2.516 A, ordered.

## Structure

- Formula: FeNi
- Space group: P4/mmm (#123)
- Lattice: a 2.516, b 2.516, c 3.559 Å; α 90, β 90, γ 90°
- Atoms in the cell: 2
- Volume: 22.529 ų
- Density: 8.442 g/cm³

## Contents

```cif
# generated using pymatgen
data_FeNi
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   2.51600000
_cell_length_b   2.51600000
_cell_length_c   3.55900000
_cell_angle_alpha   90.00000000
_cell_angle_beta   90.00000000
_cell_angle_gamma   90.00000000
_symmetry_Int_Tables_number   1
_chemical_formula_structural   FeNi
_chemical_formula_sum   'Fe1 Ni1'
_cell_volume   22.52938110
_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
  Fe  Fe0  1  0.00000000  0.00000000  0.00000000  1
  Ni  Ni1  1  0.50000000  0.50000000  0.50000000  1
```

## Use it

- Download: https://database.ouro.foundation/storage/v1/object/public/public-files/54c0d951-6a86-437f-b49f-619df8f23cb3/01a0713e-c1d5-735d-b8fa-b84a28ca8bee.cif?v=1788606333619
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- From Python: `ouro.files.retrieve("489aa4c5-0c40-4efe-a178-031fc0163811")`