An extensible and portable file format for electronic structure and crystallographic data

Gonze, Xavier [UCL] Almbladh, C.-O. Cucca, A. Caliste, D. Freysoldt, C. Marques, M. Olevano, Valério [UCL] Pouillon, Y. Verstraete, Matthieu [UCL] et al.[show all]

In order to allow software applications to interact and exchange data, file format specifications are mandatory. Widely agreed file format specifications are still lacking in the field of first- principles calculations of material properties. One of the (numerous) objectives of the European Network of Excellence “NANOQUANTA” (that is about to launch the “European Theoretical Spectroscopy Facility”) is precisely to specify file formats, for the contents that are relevant to the scientific activity of its constituent nodes. The present article gives an overview of the agreed specifications, relevant for selected content (crystallographic/density/potential/wavefunctions). The specification relies on the NetCDF library, widely used in many different scientific communities. It is a binary format, that provides complete portability of the files accross languages (C/C++/Fortran/...) and platforms (big/little-endian is irrelevant). The files are addressed by content, bringing in the additional advantages of extensibility and automatic backward compatibility. Different software applications already implement this specification, for which a specific I/O library has been developed. It is hoped that it will be implemented in other software projects, or (at least) will be the basis of even better file format specifications.