Experimental Results Related to the Normal-Incommensurate Phase Transition in A2MX4 Compounds
Inelastic neutron scattering results taken in the incommensurate phase of K2SeO4 show that the phase mode response is over-damped at low q wave-vector. A rather complete set of data obtained at 120 K, 110.5 K, 100 K, 96 K tends to demonstrate that the phase mode dispersion curve exhibits a gap at q = 0 and is relatively insensitive to temperature. The present results can be related to available Raman data. A single crystal neutron diffraction experiment has been carried out at 588 K in the normal phase of K2ZnCl4. In refining the data we tested two models: a two-position, split-atom harmonic model (R = .026) and an ordered anharmonic model (R = .019). For Cl atoms anharmonic temperature factors based on the Gram-Charlier expansion have been refined up to fourth order.
KeywordsPhase Mode Inelastic Neutron Se04 Group Dynamical Structure Factor Incommensurate Phasis
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- 2.H. Poulet, R. M. Pick, Journal of Physics C14, 2675 (1981).Google Scholar
- 7.V. A. Golovko and A. P. Levanuyk, JETP 54, 1217 (1981).Google Scholar
- 8.V. Dvorak and J. Petzelt, Journal of Physics, C11, 4827 (1978).Google Scholar
- 10.R. Currat, L. Bernard, and P. Delamoye, Incommensurate Phases in Dielectrics. 2 Materials, 161 (1986).Google Scholar
- 12.S. R. Andrews and H. Mashiyama, Journal of Physics C16, 4985 (1983).Google Scholar
- 19.M. Quilichini and J. Pannetier, Acta Crystallogr. B39, 657 (1983).Google Scholar