Isotropic Compton profiles for a set of model structures comprising water molecules and isoelectronic neon atoms have been calculated using density-functional theory. We consider dimers at different intermolecular separations and clusters with a central water molecule surrounded by a coordination shell of 1-4 water molecules or neon atoms. For intermolecular distances typical of ice, the model structures lead to oscillations in the profile as compared with the profile of the corresponding free molecules/atoms. The isotropic Compton profile is shown to contain fundamental information on the local coordination in terms of the coordination number and distance of the molecules in the first coordination shell. In addition, we show that changes in the intramolecular O-H bond length of a free water molecule have an effect on the shape of the profile.

• Received 24 February 2004

DOI:https://doi.org/10.1103/PhysRevB.70.125413