Structure and dynamics of maleic anhydride

We have carried out a comprehensive characterization of the structure and dynamics of maleic anhydride using experimental (single-crystal neutron diffraction, infrared, Raman and inelastic neutron scattering (INS) spectroscopies) and computational methods (AM1 and two levels of density functional theory). The structure is largely in agreement with previous work, although with more accurate atomic positions. However, the report of an unusually short C=C bond length is not supported by this work. The combination of ab initio results and INS spectra has confirmed the assignments of the internal modes. In addition, the complete lattice mode region is observed and assigned for the first time. Force fields derived by empirical means and from the ab initio data have been obtained and show differences, although both accurately predict the INS spectrum.