“…This refined well, and the hydrogen atom density found progressively to order into configuration A as the temperature is lowered, confirming A as the lower energy configuration. A similar experiment was carried out on another benzoic acid derivative, p-chlorobenzoic acid [81], at eight temperatures (20,40,80,100,133,200, 250 and 296 K), in an experiment requiring just 5 days of beam time. The structural evolution is shown in figure 10, again showing the characteristic elongation of the thermal ellipsoid of the hydrogen-bonded H atom as the temperature increases.…”