Structural modulation observed in Rb₂ZnCl₄

Abstract

Abstract Amplitudes of the modulation waves in Rb2ZnCl4 in the incommensurate and commensurate phases are estimated on the basis of the crystal structures at several temperatures in the normal phase, at 233 K in the incommensurate phase and at 146 K in the commensurate phase. The incommensurate structure projected onto the three-dimensional section was examined by means of de Wolff's construction. We obtain large modulation amplitude of about 0.4 Å for the Cl atoms, while small amplitude not more than 0.1 Å for the remaining atoms. It is concluded that the disordered motion of the atoms observed in the normal phase is transformed into the modulation waves in the lower-temperature phases dominating basically the nature of the structural modulation.