Compton scattering and the character of the hydrogen bond in ice I-h

Compton scattering is an experimental technique which probes the electron m omentum density. Here we present a method which allows the calculation of t he Compton profile using the formalism of the maximally localized Wannier f unctions. We applied this method to analyze recent experimental measurement s of the anisotropy component of the Compton profile which have been interp reted as the signature of the partial covalent character of the hydrogen bo nd in ice I-h. We are able to reproduce well the experimental results, howe ver we do not find evidence of a covalent nature of the hydrogen bond. In f act our analysis shows that, although the wave functions in ice I-h have a quantum-mechanical, multicenter character, this gives rise to an antibondin g, repulsive interaction between neighboring water molecules. Application t o our technique to other, nonhydrogen bonded systems, and analysis of the c orresponding Compton scattering profile anisotropy, gives further support t o our interpretation. (C) 2001 American Institute of Physics.