Satellite X-ray scattering and structural modulation of thiourea

Abstract

Integrated intensities have been measured of the satellite x-ray scatterings which appear in the intermediate phases II, III and IV of thiourem a. The structural modulation which causes the satellite scattering is assumed to be a sinusoidal transverse wave of atomic shifts with the wave number vector parallel to the c axis. Parameters which characterize the modulation at -86°C are determined by a least squares calculation, and agreement is obtained between the observed and calculated scattering amplitudes with the discrepancy factor R of 0.16. Intensities of several Bragg and satellite scatterings have been measured as functions of temperature by a single crystal diffracto meter and expression on the temperature dependence of the modulation parameters are deduced.