Evidence for Elastic Disorder in the Elastically Ordered Phase of KCN

We have obtained evidence from ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ NMR measurements that the C${\mathrm{N}}^{-}$ ion in the elastically ordered phase of KCN is misoriented slightly with respect to the orthorhombic $b$ axis. This misorientation varies randomly over the lattice, averaging to zero on a macroscopic scale. The misorientations are manifested through small-angle C${\mathrm{N}}^{-}$ reorientations which contribute to the spin-lattice relaxation time $T_1$ of the ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ nuclei, via dipolar interactions and chemical shift anisotropy.