---
license: llama3.1
base_model: meta-llama/Llama-3.1-8B-Instruct
library_name: transformers
pipeline_tag: text-generation
language:
- en
tags:
- chemistry
- molecular-geometry
- conformer-generation
- smiles
- z-matrix
- geom
- llama
- axolotl
- arxiv:2607.13350
datasets:
- GEOM
---

# Llama-3.1-8B-GeomLlama-zmatrix

**Built with Llama. Built with Axolotl.**

GeomLlama-zmatrix is a fine-tune of **Llama-3.1-8B-Instruct** that generates
3D molecular conformer geometries directly from a SMILES string, emitting each
structure as a **Fenske–Hall Z-matrix** (internal coordinates: bond length, bond
angle, dihedral, referenced to previously placed atoms). It is one of two models
from our paper; the companion model, [Llama-3.1-8B-GeomLlama-xyz](https://huggingface.co/THGLab/Llama-3.1-8B-GeomLlama-xyz),
emits Cartesian XYZ coordinates instead.

The model was trained jointly ("hybrid") on **GEOM-QM9** and **GEOM-Drugs**, so it
covers both small molecules and larger drug-like molecules with a single set of
weights.

## Quick start

The model was trained in the Alpaca instruction format. Reproduce the exact
inference prompt used for the paper's numbers:

```python
import torch
from transformers import AutoModelForCausalLM, AutoTokenizer

model_id = "THGLab/Llama-3.1-8B-GeomLlama-zmatrix"
tok = AutoTokenizer.from_pretrained(model_id)
model = AutoModelForCausalLM.from_pretrained(model_id, torch_dtype=torch.bfloat16, device_map="auto")

smiles = "Cc1cccc(CSc2nnnn2-c2ccccc2)c1"
prompt = (
    "### Instruction:\n"
    "You can generate accurate molecular coordinates from a prompt "
    "containing a SMILES string.\n\n"
    "### Input:\n"
    "Generate a realistic equilibrium geometry for the molecule with the "
    f"following SMILES string in Fenske-Hall Z-matrix format: {smiles}\n\n"
    "### Response:\n"
)

inputs = tok(prompt, return_tensors="pt").to(model.device)
out = model.generate(**inputs, max_new_tokens=3072, do_sample=True, temperature=1.0, top_p=0.95)
print(tok.decode(out[0][inputs.input_ids.shape[1]:], skip_special_tokens=True))
```

Sample many completions per SMILES (each is one candidate conformer) to build a
conformer ensemble. `T=1.0, top_p=0.95` and `T=1.2, top_p=0.95` are good defaults.

### Output format

Each line places one atom. The first token is the element; the remaining tokens
are the internal coordinates relative to earlier atoms:

```
O 1                          # atom 1: reference origin
C 1 1.388                    # atom 2: bonded to atom 1 at 1.388 Å
H 2 1.090 1 105.769          # atom 3: bond to 2, angle to 1
C 2 1.547 1 117.304 3 129.0  # atom 4: bond, angle, dihedral
...
```

Atoms are emitted in an arbitrary order with **no atom labels or connectivity
block** — the model learns geometry from the SMILES alone. Parse the Z-matrix back
to Cartesian coordinates with a standard NeRF/internal-to-Cartesian routine.

> View z-matrix or xyz coordinates easily at
> [doublemolview.streamlit.app](https://doublemolview.streamlit.app).

## Training

- **Base:** meta-llama/Llama-3.1-8B-Instruct
- **Framework:** [Axolotl](https://github.com/axolotl-ai-cloud/axolotl)
- **Method:** LoRA (r = 32, α = 16, dropout 0.05, all linear layers), merged into the base weights
- **Epochs:** 4 · **LR:** 3e-4, cosine · **Optimizer:** adamw_bnb_8bit
- **Sequence length:** 4096, sample packing · **Precision:** bf16
- **Data:** GEOM-QM9 + GEOM-Drugs, Fenske–Hall Z-matrix targets (`ori_fh`), plus the
  [Alpaca](https://huggingface.co/datasets/tatsu-lab/alpaca) instruction dataset for
  general-instruction rehearsal

## Citation

Paper: *How Well Can Frontier Large Language Models Generate Structures? High Quality
Prediction of Molecular Geometries with Help from Fine-Tuning* —
[arXiv:2607.13350](https://arxiv.org/abs/2607.13350). Please cite the paper and the
underlying GEOM dataset (Axelrod & Gómez-Bombarelli, *Scientific Data*, 2022) if you
use this model.

```bibtex
@misc{cavanagh2026geomllama,
  title         = {How Well Can Frontier Large Language Models Generate Structures?
                   High Quality Prediction of Molecular Geometries with Help from Fine-Tuning},
  author        = {Cavanagh, Joseph M. and Arnold, Jonathan B. and Alteri, Giovanni Battista
                   and Gritsevskiy, Andrew and Head-Gordon, Teresa},
  year          = {2026},
  eprint        = {2607.13350},
  archivePrefix = {arXiv},
  url           = {https://arxiv.org/abs/2607.13350}
}
```

## License

Governed by the [Llama 3.1 Community License](https://github.com/meta-llama/llama-models/blob/main/models/llama3_1/LICENSE).
By using this model you agree to its terms. Built with Llama.