Data Libraries

OpenMC uses an HDF5-based data format for storing cross sections, angle-energy distributions, and other data that are needed during a simulation. These HDF5 files can be generated from ACE files, which is the format used by many other Monte Carlo codes including MCNP and Serpent, using OpenMC’s Python API. However, to avoid the burden of having to generate a library yourself, this website contains pre-generated HDF5 data libraries that can simply be downloaded and used right away.

The scripts that were used to generate the libraries here can be found in the openmc-dev/data GitHub repository. If you are experiencing a problem with one of the data libraries or believe you have found a bug in the data conversion, please feel free to open an issue on the repository.


For a given library, download and unpack the archive in a desired location. Inside the directory that is extracted is a file called cross_sections.xml. Set your OPENMC_CROSS_SECTIONS environment variable to the absolute path of this file and then it will be recognized when you run OpenMC.

Format Versioning

From time to time, the HDF5 format used by OpenMC may be changed in ways that are not backwards compatible. While the development team tries to avoid this if possible, sometimes it is necessary for reasons of accuracy and performance. The libraries you’ll find here work with version 0.11.0 of OpenMC and later. In the future, if the HDF5 format changes, updated libraries will be made available here.