JANPA: An open source cross-platform implementation of the Natural Population Analysis on the Java platform

The algorithms for constructing Natural Atomic Orbitals (NAOs) from a reduced one-particle density matrix as well as for Natural Population Analysis (NPA) are reviewed and their novel independent cross-platform open-source implementation on Java platform, a JANPA package, is presented. The package consists of three programs: two of them generate MOLDEN files from the output of popular quantum chemistry packages (PSI4, ORCA, NwChem, Gaussian, GAMESS-US, etc.), and one program performs NAO/NPA transformations taking these data as an input. The developed programs can be freely obtained at http://janpa.sourceforge.net.