Inelastic neutron scattering and DFT study of potassium hydrogen phthalate

Inelastic neutron scattering and solid state quantum chemistry calculations are applied to investigate the lattice vibrations in crystalline potassium hydrogen phthalate containing very short intermolecular OH⋯O hydrogen bond (2.529 Å). The inelastic neutron scattering spectrum is interpreted in the energy range 30–3500 cm−1 using the density function theory approach within the harmonic approximation. The one-dimensional potential of the proton moving along the short OH⋯O bond is mapped and a considerable contribution of anharmonicity (about 24%) to the antisymmetric OHO stretching vibration is calculated.