chem-sorption-gcmc

chem-sorption-gcmc is a skill for Claude Code, Codex from learningmatter-mit/AtomisticSkills. It costs 30 tokens per session (1,040 once invoked), scanned A, original, MIT.

A simulation workflow for estimating how much gas a porous material can hold at a chosen temperature and pressure. It uses Grand Canonical Monte Carlo, a computer method that models particles entering and leaving a material, with machine-learned force calculations.

In plain words
What is it for?
Use it to run gas-adsorption simulations for porous materials and examine uptake under selected conditions.
Why use it?
It provides a way to study gas adsorption in porous structures, including single gases or mixtures, using a relaxed structure as the starting point.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: installed under .agents/ (shared by several agents).

Needs its repository: it runs a file that does not travel with it, so clone the repository first. The line is --output-dir ./results/single_gcmc.

Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo
git clone --depth 1 https://github.com/learningmatter-mit/AtomisticSkills
agentmods
npx agentmods add skills/learningmatter-mit/atomisticskills/chem-sorption-gcmc

Made for: Claude Code, Codex.

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README.md
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<a href="https://agentmods.dev/skills/learningmatter-mit/atomisticskills/chem-sorption-gcmc"><img src="https://agentmods.dev/badge/skills/learningmatter-mit/atomisticskills/chem-sorption-gcmc.svg" alt="Measured on agentmods" height="20"></a>
Per session 30 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,040 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 5.1 $0.00030 $0.01040
Opus 5 $0.00015 $0.00520
Sonnet 5 $0.00006 $0.00208
Haiku 4.5 $0.00003 $0.00104

Measured 6d ago against content hash 92be87844bba, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

chem-sorption-gcmc 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 6d ago.

The scan reads SKILL.md. This mod also ships 11 executable files (examples/test_gcmc.sh, scripts/ase_mc/__init__.py, scripts/ase_mc/ensembles.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-sorption-gcmc/SKILL.md · 90 lines

How it starts

The opening of the file, as written. The whole thing — 90 lines — stays where its author put it; the contents beside it link to each section on GitHub.

chem-sorption-gcmc

Goal

To predict the macroscopic adsorption uptake of a gas (or gas mixture) in a porous material at a specific temperature and pressure. The skill relies on Grand Canonical Monte Carlo (GCMC) simulations where the host-guest and guest-guest interactions are calculated using a Machine Learning Interatomic Potential (MLIP: MACE, FairChem, MatGL).

Prerequisites

  • Input: A relaxed framework structure in CIF (or XYZ) format. The structure should ideally be processed by chem-sorption-relax to ensure proper supercell dimensions.
  • Conda environment: Depends on the MLIP used (e.g., fairchem-agent, mace-agent, matgl-agent).

Instructions

  1. Perform Single-Component GCMC (Optional): If you are investigating a single gas species, use run_gcmc.py.
# Env: fairchem-agent (or other MLIP-specific env)
python .agents/skills/chem-sorption-gcmc/scripts/run_gcmc.py \
    --cif path/to/relaxed_supercell.cif \
    --calculator fairchem \
    --model-name uma-s-1p1 \
    --task-name omol \
    --steps 50000 \
    --temperature-K 298 \
    --pressure-bar 1.0 \
    --adsorbate CO2 \
    --output-dir ./results/single_gcmc
  1. Perform Multi-Component GCMC (Optional): If you are simulating a gas mixture (e.g. flue gas separation 15% CO2 / 85% N2), use run_gcmc_multi.py.
# Env: fairchem-agent
python .agents/skills/chem-sorption-gcmc/scripts/run_gcmc_multi.py \
    --cif path/to/relaxed_supercell.cif \
    --calculator fairchem \
    --model-name uma-s-1p1 \
    --task-name omol \
    --steps 50000 \
    --temperature-K 298 \
    --gases CO2 N2 \
    --y 0.15 0.85 \
    --p-total-bar 1.0 \
    --output-dir ./results/multi_gcmc

Key Parameters

  • --cif: Path to the relaxed host framework.
  • --calculator: The backend MLIP (fairchem, mace, matgl).
  • --model-name: Name or path to the MLIP weights (e.g., uma-s-1p1.pt, MACE-MH-1).
  • --task-name: Optional, required by some models (omol for UMA and MACE-MH).
  • --steps: Number of Monte Carlo steps (minimum 50,000 recommended for equilibration).
  • --temperature-K: Sim temperature.
  • --pressure-bar (Single): Gas pressure in bar.
  • --p-total-bar (Multi): Total mixture pressure in bar.
  • --gases / --y (Multi): Species list and corresponding mole fractions in the vapor phase.

Read the full file on GitHub · 90 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. 6d ago First seen · 90 lines · 30 tokens per session scan A 92be87844bba

Subscribe to this mod's changes

chem-sorption-gcmc is a skill published in the GitHub repository learningmatter-mit/AtomisticSkills (161 stars, last pushed 3d ago), licensed MIT. It adds 30 tokens to every session and 1,040 once invoked, about $0.0002 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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