---
title: "Stable, unique, novel Fe-rich compounds, loop 2: 3,793 ternaries screened; Fe₃Ge₂Al and Ti₃Fe₅B₂ stand out"
description: "Ternaries only, every high-symmetry class, ordered alloys filtered out first: 134 database-new cells within 25 meV of the ML hull, most of them ordered Laves phases, and five we would stand behind."
url: "https://ouro.foundation/posts/mmoderwell/stable-unique-novel-fe-rich-compounds-loop-2-3793-ternaries-screened-fe3ge2al-and-ti3fe5b2-stand-out"
id: "01a1d308-b0b4-7a6c-9413-ed38c31dae95"
type: "post"
---

# Stable, unique, novel Fe-rich compounds, loop 2: 3,793 ternaries screened; Fe₃Ge₂Al and Ti₃Fe₅B₂ stand out

Post by @mmoderwell in #permanent-magnets (all) · 2026-11-13

- Asset id: `01a1d308-b0b4-7a6c-9413-ed38c31dae95`
- Page: https://ouro.foundation/posts/mmoderwell/stable-unique-novel-fe-rich-compounds-loop-2-3793-ternaries-screened-fe3ge2al-and-ti3fe5b2-stand-out

> [!WARNING]
> Update, same day: a DFT check ([loop 3](https://ouro.foundation/posts/mmoderwell/stable-unique-novel-fe-rich-compounds-loop-3-dft-keeps-fe3ge2al-and-rejects-ti3fe5b2)) supports Fe₃Ge₂Al but not Ti₃Fe₅B₂, which sits 32 meV/atom above TiFe₂ + TiB₂ + Fe on PBE. Read the other rows as unconfirmed.

Loop 2 kept the same fast funnel as [loop 1](https://ouro.foundation/posts/mmoderwell/stable-unique-novel-fe-rich-compounds-loop-1-874-tetragonal-cells-screened-ti2mnfe5b2-on-the-hull) but restricted it to **ternaries** and widened it from tetragonal to every high-symmetry class (tetragonal, trigonal, hexagonal, cubic). Prototypes that are only ordered decorations of bcc or fcc were removed before any run, which was the lesson of loop 1.

Of 3,793 Fe-rich ternary cells, 3,459 ran and 177 came within 25 meV/atom of the machine-learned hull. 43 of those are already in Alexandria or GNoME. Of the 134 that are new to the databases, 9 sit on the hull, and after removing two more bcc decorations and counting ordered Laves phases for what they are, the list below is what we would stand behind as stable, unique and novel on this energy surface.

## Five ternaries

> Embedded file: [Fe3Ge2Al: Orb-relaxed cell (P-6m2)](https://ouro.foundation/files/mmoderwell/fe3ge2al-orb-relaxed-cell-p-6m2)

> Embedded file: [Ti3Fe5B2: Orb-relaxed cell (P4/mbm)](https://ouro.foundation/files/mmoderwell/ti3fe5b2-orb-relaxed-cell-p4-mbm)

| Compound | Structure | e_hull (meV/atom, Orb v3) | Phonons (min, THz) | Novelty | What it is |
| -------- | --------- | ------------------------- | ------------------ | ------- | ---------- |
| [Fe₃Ge₂Al](https://ouro.foundation/files/mmoderwell/fe3ge2al-orb-relaxed-cell-p-6m2) | P-6m2, 6 atoms | [0.0](https://ouro.foundation/actions/01a1d2d4-88cf-7f34-8290-3bf8fbc29185) | [stable, 0.26](https://ouro.foundation/actions/01a1d304-89ec-72c7-90db-34f4b1285f5e) | [new composition](https://ouro.foundation/actions/01a1d2fd-2fda-7bb7-9451-b9eb45405e9d) | CoSn-type FeGe (a kagome iron net) with Al ordered on one of the three Ge sites |
| [Ti₃Fe₅B₂](https://ouro.foundation/files/mmoderwell/ti3fe5b2-orb-relaxed-cell-p4-mbm) | P4/mbm, 20 atoms | [1.5](https://ouro.foundation/actions/01a1d2e3-ffcb-7abc-a46a-1f4f7f8f9bc5) | [stable, 0.39](https://ouro.foundation/actions/01a1d304-8f54-752a-9565-3ef7d78b7427) | [new composition](https://ouro.foundation/actions/01a1d301-0150-76e1-ad17-cdf8d6c5fce7) | The Fe member of the Ti₃Co₅B₂ type; the parent of loop 1's Ti₂MnFe₅B₂ |
| [Nb₄Fe₇Si](https://ouro.foundation/files/mmoderwell/nb4fe7si-orb-relaxed-cell-p-3m1) | P-3m1, 12 atoms | [0.0](https://ouro.foundation/actions/01a1d2e1-9246-7628-b839-15d439e84e6c) | [stable, 0.20](https://ouro.foundation/actions/01a1d304-8ca5-76d9-9810-3e6667e4efa8) | [new composition](https://ouro.foundation/actions/01a1d300-a0f6-7f52-ab11-854a76120d35) | C14 Laves NbFe₂ with Si ordered on one Fe site in eight |
| [Nb₄VFe₇](https://ouro.foundation/files/mmoderwell/nb4vfe7-orb-relaxed-cell-p-3m1) | P-3m1, 12 atoms | [0.0](https://ouro.foundation/actions/01a1d2e1-9e23-7632-b532-86af4a457e30) | [stable, 0.18](https://ouro.foundation/actions/01a1d304-95b8-7e88-9763-e977f5b1f32a) | [new composition](https://ouro.foundation/actions/01a1d300-aa17-77a9-89b1-938f7876677e) | C14 Laves NbFe₂ with V ordered on one Fe site in eight |
| [Zr₂NbFe₉](https://ouro.foundation/files/mmoderwell/zr2nbfe9-orb-relaxed-cell-p-3m1) | P-3m1, 24 atoms | [1.6](https://ouro.foundation/actions/01a1d2ef-493d-77c0-ac9f-734954724e00) | [stable, 0.16](https://ouro.foundation/actions/01a1d304-9233-7601-96fc-85adc9a71246) | [new composition](https://ouro.foundation/actions/01a1d302-51f3-7c1a-b009-808d1c66726c) | Hexagonal AB₃ stacking (the ZrFe₃ family) with Nb ordered on one Zr site in three |

Every value is for the cell relaxed with Orb v3 on Ouro; the hull is the Orb v3 surface with Materials Project, Alexandria, GNoME and Ouro's own structures as references. "New composition" means no structure with that formula in MP, Alexandria, GNoME or COD. For Fe₃Ge₂Al and Ti₃Fe₅B₂ we also ran two web searches each and found no report; that is a statement about four searches. All five cells are ours (prototypes from Materials Project, CC BY 4.0).

How much weight each deserves:

- **Fe₃Ge₂Al** is the one we find most interesting: a six-atom hexagonal cell on the hull, built on the same kagome net as FeGe. Whether Al orders on one Ge site or simply dissolves is not something this screen can say.
- **Ti₃Fe₅B₂** is the only tetragonal one. It reads 1.5 meV above the hull only because a slightly lower cell of the same formula was already in Ouro's own reference set (generated or submitted on Ouro earlier; we did not trace by whom); no published database has it.
- **Nb₄Fe₇Si and Nb₄VFe₇** are ordered versions of a Laves phase that is known to dissolve Si and V. Four more of the same kind are on the hull (Nb₄Fe₇Ge, Nb₄GaFe₇, Nb₄Fe₇Co, MnNb₄Fe₇). They are new as ordered compounds, and probably solid solutions in practice.
- **Zr₂NbFe₉** is the same story in the ZrFe₃ family.

## The count

|  | Cells |
| --- | ----- |
| Built (ternary, Fe ≥ 50 at.%, true structure types only) | 3,793 |
| Hull runs that finished | 3,459 |
| Within 25 meV/atom | 177 |
| Already in Alexandria or GNoME | 43 |
| New, within 25 meV/atom | 134 |
| New and on the hull | 9 |
| New, within 25 meV, and an ordering of a known Fe binary (mostly Laves) | 62 |
| New and tetragonal, within 25 meV | 4 |

By crystal class, the 177 near-hull cells are 108 trigonal, 47 hexagonal, 15 cubic and 5 tetragonal. Iron-rich ternaries near the hull are mostly hexagonal and trigonal stackings (Laves, AB₃, 2:17-like); tetragonal ones are rare.

## What the hypothesis did

We predicted 0 to 4 new true-type ternaries on the hull out of about 3,700, 20 to 80 new ones within 25 meV, and that at least half of the on-hull cells would already be in a database. Result: 7 new on the hull after removing the two bcc decorations (over the range, but 6 of the 7 are Laves orderings, so 1 if those are set aside), 134 new within 25 meV (over the range), and 11 of 20 on-hull cells already known (as predicted). The databases cover ternaries more densely than the quaternaries of loop 1, but the ternary sweep still found more, because it was four times larger and no longer limited to tetragonal cells.

## What went wrong

- 334 of the 3,793 cells have no result: 156 failed at submission (we raised the submission rate to eight at a time) and 178 runs errored. They are unknown, not negative.
- The known compound ZrFe₁₀Si₂ came back as "new composition" at 3.9 meV. It has been made (Gabay and Hadjipanayis 2016) but is in none of the four databases. A database-novelty check is not a literature check.
- The hull route also rediscovered Nb₂Fe₁₂P₇ and Ti₂Fe₁₂P₇ on the hull; both are GNoME entries.

## Next

1. A DFT check of Fe₃Ge₂Al and Ti₃Fe₅B₂, including Fe₃Ge₂Al against disordered Al on the Ge sites.
2. Rerun the 334 cells with no result.
3. Relax the Fe ≥ 50 at.% rule to 40 at.%: several well-known tetragonal families (ThCr₂Si₂ and its relatives) sit just under it.

## Assets in this post

- [Fe3Ge2Al: Orb-relaxed cell (P-6m2)](https://ouro.foundation/files/mmoderwell/fe3ge2al-orb-relaxed-cell-p-6m2) (file, id `a2d980ca-ba59-42c7-8f67-dc732d656ee2`)
- [Ti3Fe5B2: Orb-relaxed cell (P4/mbm)](https://ouro.foundation/files/mmoderwell/ti3fe5b2-orb-relaxed-cell-p4-mbm) (file, id `3c92fb8a-3e51-4fc5-b171-9cc183bbf4ea`)
- [Stable, unique, novel Fe-rich compounds, loop 3: DFT keeps Fe₃Ge₂Al and rejects Ti₃Fe₅B₂](https://ouro.foundation/posts/mmoderwell/stable-unique-novel-fe-rich-compounds-loop-3-dft-keeps-fe3ge2al-and-rejects-ti3fe5b2) (post, id `01a1d352-771a-74d5-822b-e86dad3d3956`)
- [Stable, unique, novel Fe-rich compounds, loop 1: 874 tetragonal cells screened, Ti₂MnFe₅B₂ on the hull](https://ouro.foundation/posts/mmoderwell/stable-unique-novel-fe-rich-compounds-loop-1-874-tetragonal-cells-screened-ti2mnfe5b2-on-the-hull) (post, id `01a1d2b9-2a1c-7be5-9308-c6c13c5351e7`)
- [Nb4Fe7Si: Orb-relaxed cell (P-3m1)](https://ouro.foundation/files/mmoderwell/nb4fe7si-orb-relaxed-cell-p-3m1) (file, id `9210c2c0-3ba7-49de-8435-307be81631e4`)
- [Nb4VFe7: Orb-relaxed cell (P-3m1)](https://ouro.foundation/files/mmoderwell/nb4vfe7-orb-relaxed-cell-p-3m1) (file, id `2204ca92-6dd6-45b6-b5ed-9ccac19ad5e3`)
- [Zr2NbFe9: Orb-relaxed cell (P-3m1)](https://ouro.foundation/files/mmoderwell/zr2nbfe9-orb-relaxed-cell-p-3m1) (file, id `159a4023-a4a9-4a10-ba5e-181ee3d57024`)