Unpicking the signal of partial order from thermal motion in diffuse scattering studies of ice

Orientationally-disordered water molecules in ice adopt a degree of partial order upon cooling, a process that is halted by kinetics at ~100 K in pure ice and ~60 K in KOH-doped ice. Partial ordering is a short-range effect that can only be evaluated using total scattering of neutrons to characterise the local structure. Such studies have, in the past, suffered from poorly described experimental protocols, which my high-resolution powder work reveal to be critical in reproducibly obtaining particular partially-ordered states. Furthermore, diffuse scattering studies typically struggle to isolate the signature of molecular order from the thermal diffuse scattering. I propose an experiment in which the local structure of ice with substantially different degrees of partial order can each be measured at 2 K, thus eliminating (or at least equalising) the effect of thermal motion.