Hydrogen-Atom Ordering in Lead Hydrogen Arsenate Monitored by Neutron Time-of-Flight Laue Diffraction using...

The ordering of the hydrogen atom in a single crystal of lead hydrogen arsenate in the temperature range 320 to 80 K is described. The details of the ordering at small temperature steps are determined from single frames of data collected using the neutron time-of-flight Laue method. The constrained refinements obtained from these data yield lower precision than full data sets but allow the ordering to be characterized rapidly and reliably. This is the first example of the use of this single-frame method of monitoring such phase transitions. The approach used here with neutrons, stimulated in part by synchrotron Laue diffraction, will be of interest for all time-resolved experiments with synchrotron radiation or neutrons.