Migration of the proton in the strong O-H.O hydrogen bond in urea-phosphoric acid (1/1).
The structure of urea-phosphoric acid is reported at a large number of temperatures in the range 150-335 K from neutron diffraction data collected using a novel multiple single-crystal data collection method. The work focuses on the behaviour of the H atom involved in the short strong O-H.O hydrogen bond in this material. The position of this atom is shown to vary significantly, by around 0.035 A, as a function of temperature, becoming effectively centred at the highest temperatures studied. This result, only accessible due to the accurate determination of H-atom parameters by neutron diffraction, has implications for the potential governing the hydrogen bond.
Wilson
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ISIS Department, CLRC Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, England. c.c.wilson@rl.ac.uk