STUDIES ON THE COOPERATIVE PHENOMENON OF X-RAY CRITICAL SCATTERING NEAR PHASE TRANSITIONS IN SOLIDS.
Final tech. rept., 1 Dec 62-30 Nov 63,
MADRID UNIV (SPAIN)
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The disorder of the paraelectric phase of NaNO2 has been evidenced from the existence at about 185 C of x-ray diffuse scattering sheets normal to the polar axis. It has been shown that these sheets can be explained as arising from long small domains so called cigarrillos of about 30 A with ferroelectric structure statistically oriented parallel or antiparallel to the polar axis. This posiional disorder alone with correlations cannot explain the observed diffuse scattering sheet near to the 002 reflection, even if correlated librations are intrduced. Calculations and Fraunhoier patterns of two dimensional models with statistical point structures prove that the domains oscillate parallel to the polar axis as rigid entities. Much of the analysis has been carried out with the help of the Q-function calculated andexperimentally produced with a twodimensional folding machine. Author