I. Aramburu et al., TEMPERATURE-DEPENDENCE OF THE STATIC DISTORTION IN INCOMMENSURATE DISPLACIVE PHASES AND ITS EFFECT ON THE DIFFRACTION PATTERN .2. SATELLITEREFLECTIONS, Acta crystallographica. Section A, Foundations of crystallography, 53, 1997, pp. 334-340
The effect on satellite reflections of the temperature variation of th
e static structural modulation in incommensurate phases is studied. A
structural model is introduced that includes the anharmonicity describ
ed by the soliton density and follows the assumptions and predictions
of the Landau theory generalized to incommensurate phases. Within thes
e premises, a simulation of the diffraction pattern as a function of t
emperature of Rb2ZnCl4 has been carried out. It is shown that the inte
nsity of satellites does not always decrease monotonically with their
order and its temperature dependence varies, depending on the satellit
e, so that it cannot be reduced to a common effective power law. Satel
lites of first order, for instance, can decrease or increase near the
lock-in transition, depending on the particular reflection considered.
A simple method for measuring the soliton density is proposed that is
based on the expected correlation of the intensities of close first-o
rder and higher-order satellites. Finally, the effect that high-order
harmonics can have in a standard refinement of an incommensurate struc
ture near the lock-in transition is discussed.