Compton-profile studies of amorphous and single-crystal SiO2

Compton profiles of crystalline and amorphous Si${\mathrm{O}}_2$ are compared and found to be the same within experimental error. The profiles fit a purely ionic crystalline model, ${\mathrm{Si}}^4$+${\mathrm{O}}_2^{2-}$ to within 1%. The spherical nature of the ionic model is in agreement with the very small (0.25%) anisotropy measured for the Compton profile in quartz. A general discussion is presented concerning the relationship of ionicity and anisotropy in the Compton profile.