This archive contains data on calculated electronic structure, crystal-field splitting, exchange interactions, mean-field order parameters and inelastic neutron scattering (INS) cross-section of neptunium dioxide NpO2 discussed in this manuscript. The folder structure is V0------|-- DFTHI # equilibrium volume |-- mean-field |-- INS V0-1p---|-- DFTHI # volume compressed by 1% |-- mean-field V0_1p---|-- DFTHI # volume expanded by 1% |-- mean-field Each DFTHI folder contains - Wien-2k struct file (NpO2.struct), - main output of DFT+Hubbard-I (DFT+HI) self-consistent calculations (NpO2.scf) - calculated energies, orbital, spin, and total angular and magnetic moments for the Np 5f^3 levels within the ground-state multiplet (GS_MULTIPLET) - all calculated inter-site superexchange interactions (SEI) between dipole and multipole moments of the Np ground-state quadruplet (Jeff=3/2) in the global coordination frame (V_Mult.dat). See the paper for a detailed description. The SEI for first 3 coordination shells are listed for the equilibrium volume to show their rapid decay. The cutoff for printing SEI matrices V_KK'(R) in V_Mult.dat is MAX|V_KK'(R)| < 0.002 meV. Each mean-field folder contains - mcphas.fum listing, among other data, the free and total ordering energy (col. 8 and 9, in meV per Np) as a function of temperature (col. 1, Kelvin) calculated within the mean-field approximation. - mcphas.sps listing the corresponding ordered state for each temperature. The moments are defined in the Jeff space as described in the paper. These files are output of the mcphase package (M. Rotter, www.mcphase.de). See the mcphase manual at www.mcphase.de for a more detailed description of those files. V0/INS folder contains the spherically-averaged INS cross-sections calculated within RPA as described in the paper for a set of momentum transfer values q. Each file Integrated_INS_q#.#_invA contains the cross-section for q=#.# 1/Ang. The energy transfer is in meV.