Electron momentum density and compton profiles: an accurate check of overlap models

Directional Compton profiles of single crystal LiH have been measured for the scattering vector parallel to 〈100〉 and 〈110〉. These two directions are of prime importance because 〈100〉 is the direction of the LiH molecular bond and 〈110〉 that of the interactions between ions of the same species. These measurements have been performed using X-Ray inelastic scattering with the highest ever achieved resolution. Because of Synchrotron Radiation, this technique has now reached the point of routine and reliable execution. Compton scattering is a very accurate test of calculated wave functions. Our results are compared with two different calculations. None is found to be satisfactory over the entire momentum range. Best agreement is obtained at large momentum values with a calculation where the overlap between hydrogen ions is treated, but the existing discrepancy at small momentum invites to more sophisticated models.