Proton harmonic motion in ice
10 Oct 2010



There is currently great interest in probing the quantum state of the proton in ice.




This can be revealed from the momentum distribution n(p), which is a very sensitive probe of the potential of mean force experienced by the protons in hydrogen-bonded systems. We have explored the details of n(p) in ice at T=271 K using a combination of deep inelastic neutron scattering and path-integral Car-Parrinello molecular dynamics simulations. The neutron data have been interpreted within the framework of the impulse approximation, which allows us to extract the three-dimensional n(p). Experimental and simulation data have been successfully interpreted with an anisotropic Gaussian model in which the proton essentially moves in a harmonic well along each direction, but with a marked anisotropy between motions parallel and perpendicular to the bond-stretching direction.

The proton momentum distribution in ice parallel (p||) and perpendicular (p ) to the bond-stretching direction.

D Flammini, A Pietropaolo, R Senesi, C Andreani (Università di Roma Tor Vergata, Italy), F McBride, A Hodgson (Liverpool University), L  Lin, R Car (Princeton University USA), MA Adams (ISIS)

Research date: May 2010

Further Information

Contact: Prof C Andreani,

Further reading: C Andreani et al., Adv Phys 54 (2005) 377​