Theoretical study of manganese hydrides and halides, MnXn with X = H, F, Cl, Br and n = 1-4

► The B3P86 functional is found to be reliable in predictions of molecular structures and vibrational spectra. ► The hybrid B3LYP is more reliable for energetic parameters such as heats of formation. ► We also propose several new assignments for heats of formation and ionization energies of a number of species considered.