# LeMat-Traj: A Scalable and Unified Dataset of Materials Trajectories for Atomistic Modeling

## TL;DR

LeMat-Traj is a comprehensive, standardized, and large-scale dataset of materials trajectories from DFT calculations, designed to facilitate the development of accurate machine learning interatomic potentials in materials science.

## Contribution

This work introduces LeMat-Traj, a unified and scalable dataset of over 120 million atomic configurations, with standardized formats and high-quality filtering, enabling improved MLIP training.

## Key findings

- Enhanced force prediction accuracy in ML models
- Significant reduction in training data fragmentation
- Provides a reproducible framework for dataset integration

## Abstract

The development of accurate machine learning interatomic potentials (MLIPs) is limited by the fragmented availability and inconsistent formatting of quantum mechanical trajectory datasets derived from Density Functional Theory (DFT). These datasets are expensive to generate yet difficult to combine due to variations in format, metadata, and accessibility. To address this, we introduce LeMat-Traj, a curated dataset comprising over 120 million atomic configurations aggregated from large-scale repositories, including the Materials Project, Alexandria, and OQMD. LeMat-Traj standardizes data representation, harmonizes results and filters for high-quality configurations across widely used DFT functionals (PBE, PBESol, SCAN, r2SCAN). It significantly lowers the barrier for training transferrable and accurate MLIPs. LeMat-Traj spans both relaxed low-energy states and high-energy, high-force structures, complementing molecular dynamics and active learning datasets. By fine-tuning models pre-trained on high-force data with LeMat-Traj, we achieve a significant reduction in force prediction errors on relaxation tasks. We also present LeMaterial-Fetcher, a modular and extensible open-source library developed for this work, designed to provide a reproducible framework for the community to easily incorporate new data sources and ensure the continued evolution of large-scale materials datasets. LeMat-Traj and LeMaterial-Fetcher are publicly available at https://huggingface.co/datasets/LeMaterial/LeMat-Traj and https://github.com/LeMaterial/lematerial-fetcher.