Sharing electronic structure and crystallographic data with ETSF_IO

We present a library of routines whose main goal is to read and write exchangeable files (NetCDF file format) storing electronic structure and crystallographic information. It is based on the specification agreed inside the European Theoretical Spectroscopy Facility (ETSF). Accordingly, this library is nicknamed ETSF_IO. The purpose of this article is to give both an overview of the ETSF_IO library and a closer look at its usage. ETSF_IO is designed to be robust and easy to use, close to Fortran read and write routines. To facilitate its adoption, a complete documentation of the input and output arguments of the routines is available in the package, as well as six tutorials explaining in detail various possible uses of the library routines. Program summary: Program title: ETSF_IO. Catalogue identifier: AEBG_v1_0. Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEBG_v1_0.html. Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland. Licensing provisions: Gnu Lesser General Public License. No. of lines in distributed program, including test data, etc.: 63 156. No. of bytes in distributed program, including test data, etc.: 363 390. Distribution format: tar.gz. Programming language: Fortran 95. Computer: All systems with a Fortran95 compiler. Operating system: All systems with a Fortran95 compiler. Classification: 7.3, 8. External routines: NetCDF, http://www.unidata.ucar.edu/software/netcdf. Nature of problem: Store and exchange electronic structure data and crystallographic data independently of the computational platform, language and generating software. Solution method: Implement a library based both on NetCDF file format and an open specification (http://etsf.eu/index.php?page=standardization).