CL-35 NQR STUDY OF THE INCOMMENSURATE STRUCTURAL PHASE-TRANSITION IN RB2ZNCL4

The 35Cl NQR spectra of Rb2ZnCl4 are compatible with a model where the transition at TcI = 302 K corresponds to a transformation to an incommensurate phase due to a condensation of a soft mode with q = 1 3(1-δ)c, whereas the ferro-electric transition at TcII = 192 K corresponds to an incommensurate-commensurate phase transformation with a discontinuous decrease of δ to zero. The fact that relatively sharp 35Cl NQR lines can be seen in the incommensurate phase is compatible with the possible existence of soliton-like domains of the incommensurate phase in an otherwise commensurate structure, i.e. with a strong non-linear distortion of the condensed wave. © 1979.