Anisotropic Neutron Critical Scattering in DKDP Originating from the Ice Rule by Six-States Rotator Model

Abstract

A theoretical origin of the anisotropic neutron critical scattering observed in DKDP is studied on the basis of the H 2 PO 4 dipole order-disorder model and the ice rule constraint in KDP type ferroelectrics. A radical D 2 PO 4 is assumed to take six Slater configurations described by a six states rotator. The diffused scattering intensity is given in terms of neutron scattering structure factors for respective six configurations and correlation functions among six states rotators. The scattering intensity contour in the reciprocal lattice space is numerically computed and shown to be similar to the experimental results even if the rigid ice constraint is released to some extent. Discussions are made on the controversy between the proton tunneling model and the H 2 PO 4 dipole order-disorder model from these results.