chem-react-ot

A model that predicts three-dimensional transition-state structures for a chemical reaction from reactant and product structures. A transition state is the short-lived highest-energy arrangement between them.

In plain words
What is it for?
Use it to generate candidate transition states for reactions involving non-periodic molecular structures.
Why use it?
It creates a starting transition-state structure without requiring a guessed reaction path such as nudged elastic band (NEB).

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/learningmatter-mit/atomisticskills/chem-react-ot
Any agent
npx skills add learningmatter-mit/AtomisticSkills --skill chem-react-ot
Clone the repo
git clone --depth 1 https://github.com/learningmatter-mit/AtomisticSkills

Made for: Claude Code, Codex.

Per session 17 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 832 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00017 $0.00832
Opus 5 $0.00009 $0.00416
Sonnet 5 $0.00003 $0.00166
Haiku 4.5 $0.00002 $0.00083

Measured 2d ago against content hash fcdc748b9565, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

chem-react-ot scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/generate_ts.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.agents/skills/chem-react-ot/SKILL.md · 92 lines

How it starts

The opening of the file, as written. The whole thing — 92 lines — stays where its author put it; the contents beside it link to each section on GitHub.

chem-react-ot — React-OT Transition State Generation

Goal

Generate transition state (TS) structures given reactant and product structures using the React-OT model (Optimal Transport). React-OT is a generative model that predicts TS geometries directly without requiring an initial guess path (like NEB).

Category: chemistry Environment: react-ot-agent

Key Features

  • Generative TS Prediction: Predicts 3D transition state structures from 3D reactants and products.
  • Fast Inference: Uses an ODE solver for generation, typically much faster than DFT-based NEB.
  • No Path Guess Required: Directly generates the TS structure.

Usage

1. Environment Setup

This skill requires the react-ot-agent conda environment. Ensure it is installed:

# Env: react-ot-agent
cd conda-envs/react-ot-agent
bash install.sh

2. Download Models

Before running the skill for the first time, download the pre-trained model weights:

# activate react-ot-agent first
conda activate react-ot-agent
python conda-envs/react-ot-agent/download_models.py

The checkpoint is saved to ~/.cache/react-ot/checkpoints/sb-pretrained.ckpt.

3. Generate Transition State

Run the generation script with reactant and product files (xyz, cif, pdb, etc. - anything ASE reads).

# Env: react-ot-agent
python .agents/skills/chem-react-ot/scripts/generate_ts.py \
    --reactants reactant.xyz \
    --products product.xyz \
    --output_dir results/ts_search

Arguments:

  • --reactants: Path to reactant structure file(s). Can be a single file with multiple molecules or a list of files.
  • --products: Path to product structure file(s).
  • --output_dir: Directory to save the generated TS structure (ts_generated.xyz) and trajectory (generation_traj.xyz).
  • --nfe: Number of function evaluations for the ODE solver (default: 10). Higher values might be more accurate but slower.
  • --checkpoint: Path to custom model checkpoint (optional, defaults to downloaded one).

Read the full file on GitHub · 92 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 92 lines · 17 tokens per session scan A fcdc748b9565

Subscribe to this mod's changes

chem-react-ot is a skill published in the GitHub repository learningmatter-mit/AtomisticSkills (154 stars, last pushed 7d ago), licensed MIT. It adds 17 tokens to every session and 832 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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