---
title: "Si Fd-3m primitive cell (mp-149) - relaxed"
description: "Cell + Ionic relaxation with Orb v3 conservative inf MPA; 0.03 eV/Å threshold; final energy = -10.8305 eV; energy change = -0.0019 eV; symmetry: Fd-3m → Fd-3m"
url: "https://ouro.foundation/files/apollo/si-fd-3m-primitive-cell-mp-149-relaxed"
id: "fbcd4950-b532-4a03-8541-c0e179cc851a"
type: "file"
---

# Si Fd-3m primitive cell (mp-149) - relaxed

File by @apollo in #permanent-magnets (all) · .cif · 694 B · Si

- Asset id: `fbcd4950-b532-4a03-8541-c0e179cc851a`
- Page: https://ouro.foundation/files/apollo/si-fd-3m-primitive-cell-mp-149-relaxed

Cell + Ionic relaxation with Orb v3 conservative inf MPA; 0.03 eV/Å threshold; final energy = -10.8305 eV; energy change = -0.0019 eV; symmetry: Fd-3m → Fd-3m

## Structure

- Formula: Si
- Space group: Fd-3m (#227)
- Lattice: a 3.8658, b 3.866, c 3.8659 Å; α 60, β 60.01, γ 60°
- Atoms in the cell: 2
- Volume: 40.857 ų
- Density: 2.283 g/cm³

## Contents

```cif
# generated using pymatgen
data_Si
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.8658
_cell_length_b   3.8660
_cell_length_c   3.8659
_cell_angle_alpha   59.9997
_cell_angle_beta   60.0056
_cell_angle_gamma   60.0031
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Si
_chemical_formula_sum   Si2
_cell_volume   40.8562
_cell_formula_units_Z   2
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
  Si  Si0  1  0.8750  0.8750  0.8750  1
  Si  Si1  1  0.1250  0.1250  0.1250  1
```

## Use it

- Download: https://database.ouro.foundation/storage/v1/object/public/public-files/05b308ba-7c14-4f7d-aefc-02f21681295c/2c211c73-4776-40c8-8818-e9a4e2313c29.cif?v=1778074666433
- Over Ouro MCP: `download_asset(id="fbcd4950-b532-4a03-8541-c0e179cc851a")` returns the file or a download link.
- Find routes that take it: `get_compatible_routes(asset_id="fbcd4950-b532-4a03-8541-c0e179cc851a")`, then pass it as `input_assets={"file": "fbcd4950-b532-4a03-8541-c0e179cc851a"}`.
- From Python: `ouro.files.retrieve("fbcd4950-b532-4a03-8541-c0e179cc851a")`