CHARGE-DENSITY OF MGO - IMPLICATIONS OF PRECISE NEW MEASUREMENTS FOR THEORY

A tenfold improvement in the accuracy of measured low-order structure factors for MgO has been achieved using the convergent beam electron d iffraction technique. These results allow a meaningful comparison to b e made with the latest calculations. We find that the MgO charge densi ty can be described by a superposition of spherical Mg2+ and O2- ions, but that a small nonspherical distortion of Mg and O is observable in both experiment and theory. The experimental charge distribution of O 2- is more diffuse than the theory, which may be due to the breathing effect of O2- in a vibrating lattice.