An experimental determination of the ionic state of MgO by single-crystal methods

X-ray diffraction measurements have been made of the intensities of Bragg reflexions from a single-crystal of MgO which had been neutron irradiated in order to overcome the effects of extinction. Least-squares refinement of the data in terms of a number of spherical `prepared' models shows that the best agreement is obtained for the Mg2+, O2− (+ 2 well) atomic scattering factors combined with the two isotropic temperature factors BMg = 0.346 (0.009) Å2 and Bo = 0.315 (0.010) Å2. Three different sets of powder data for MgO have been re-examined and for two of these sets of measurements the best agreement is obtained with a combination of Mg2+ and O2− (+ 2 well) atomic scattering factors, while the Mg2+, O2− (Tokonami) scattering factors gives the best fit to the third set of data. The above sets of X-ray data give various descriptions of the thermal motion in MgO and these results are compared with vibration amplitudes calculated with the use of a simple shell model which yielded the values BMg = 0.287 Å2 and Bo = 0.350 Å2 for the isotropic temperature factors.