NMR Studies on Motion of Crystalline Water Molecules in K₂Pt(CN)₄Br_0.3·3.2H₂O

Abstract

The proton NMR of crystalline water molecules in a single crystal of KCP was carried out in the temperature range from 50 K to 300 K. The NMR signals corresponding to three kinds of water molecular sites were observed. The temperature dependence of the separation of the Pake doublet was found to originate in the Iibrational or rotational motion. The potentials for the rocking and twisting oscillations are well explained by the model of a simple harmonic oscillator and the oscillation in a three-well potential, respectively. The obtained potential for the latter coincides with that for the spin-lattice model proposed by Kurihara et al. for the anomalous temperature dependence of the elastic constant C₆₆ in KCP.