No. 20111 Deposited at http://cryst.instr.yamaguchi-u.ac.jp/20111
Journal: Journal of the Physical Society Japan 80, No.4, pp.044709 (April 2011)
Title: Single-Crystal Neutron Structural Analyses of Potassium Dihydrogen Phosphate
and Potassium Dideuterium Phosphate
Authors: T. Miyoshi*, H. Mashiyama, T. Asahi, H. Kiura, Y. Noda
Affiliation: Fuculty of Science, Yamaguchi University, Yamaguchi 753-8512, Japan and
Institute of Multidiciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan
(Received December 29, 2010)
Abstract:
Single-crystal neutron structural analyses have been performed on both potassium dihydrogen phosphate (KDP) and
potassium dideuterium phosphate (DKDP) in order to discuss the isotope effect from structural viewpoints. The values
of spontaneous polarization are calculated from the refined structural parameters by the point-charge method, and the
calculated values are almost in good agreement with the experimental values of each compound. The temperature
dependences of the anisotropic atomic displacement parameters U33's and positional shifts of potassium, phosphorus,
oxygen, and hydrogen/deuterium atoms along the polar c-axis is compared between KDP and DKDP. It is concluded
that the paraelectric-ferroelectric transitions are perfectly of the improper order?disorder type in both KDP and DKDP;
the ordering of the hydrogen atom induces the spontaneous displacements of both potassium and phosphorus atoms.
The interatomic distances and angles in the paraelectric and ferroelectric phases of KDP and DKDP are also
investigated. From the result, all the structural differences seem to be caused by the difference in mass between protons
and deuterons.
Keywords: hydrogen-bond-type ferroelectrics, proton and deuteron, ferroelectric phase transition, single-crystal
structural analysis, neutron diffraction
* Corresponding author, e-mail: struct(at)yamaguchi-u.ac.jp
DEPOSITED DATA (KDP/DKDP Fdd2, 10K)