Structural studies of the monoclinic dihydrogen phosphates: A neutron-diffraction study of paraelectric CsH2PO4

The crystal structure of paraelectric CsH₂PO₄ at room temperature is presented. As suggested by the strong deuteration-dependence of the transition temperature and the distribution of quasielastic scattering, one of the hydrogen bonds is found to be very probably (97.5%) disordered, with H-H=0.48(4)Å. This work is set in the context of the interest now being shown in the group of monoclinic dihydrogen phosphates-deuterated KDP, NaDP, the ferroelectric CsDP and the presumed ferroelectric T1DP (DP denotes H₂PO₄). Recent work on these other compounds is surveyed briefly.