Mechanisms of the paraelectric to ferroelectric phase transition in RbH2PO4 probed by purely resonant x-ray diffraction

C. Richter,1,4 D. V. Novikov,1,* E. Kh. Mukhamedzhanov,3 M. M. Borisov,3 K. A. Akimova,2 E. N. Ovchinnikova,2 A. P. Oreshko,2 J. Strempfer,1 M. Zschornak,4 E. Mehner,4 D. C. Meyer,4 and V. E. Dmitrienko5 1Deutsches Elektronen-Synchrotron, DESY, Photon Science, Hamburg, Germany 2Physical Department of Moscow State University, Moscow, Russia 3RRC “Kurtchatov Institute,” Moscow, Russia 4Institut für Experimentelle Physik, TU Bergakademie Freiberg, Freiberg, Germany 5A.V. Shubnikov Institute of Crystallography, Moscow, Russia (Received 18 December 2013; revised manuscript received 25 February 2014; published 27 March 2014)