Experimental Results Related to the Normal-Incommensurate Phase Transition in A2MX4 Compounds

  • M. Quilichini
Part of the NATO ASI Series book series (NSSB, volume 166)


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.


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Copyright information

© Plenum Press, New York 1987

Authors and Affiliations

  • M. Quilichini
    • 1
  1. 1.L.P.M.T.M.Université Paris XIIIVilletaneuseFrance

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