Charge distribution of O-H ⋯ o bonds in proton-irradiated KH ₂PO₄ ferroelectrics

The mechanism of charge distribution has been probed by measuring the ¹H chemical shift on a proton-irradiated KH₂PO₄ (KDP) single crystal. For high-resolution ¹H chemical shift measurements, the CRAMPS (combined rotation and multiple pulse sequence) technique is utilized. The proton irradiation caused an increase in ¹H chemical shift that can be interpreted as an electronic charge transfer from the proton to an oxygen atom, accompanied by a displacement of the proton along the hydrogen bond. The calculated Morse potentials can be explained by using evidence of electronic instabilities related to the proton displacive features.