An investigation on the bonding in MgO, CaO, SrO and BaO from the MEM electron density distributions Original Research Article

The bonding in MgO, CaO, SrO and BaO has been studied using the electron density distribution maps obtained utilizing the reported X-ray data by the statistical approach maximum entropy method (MEM). The ionic/covalent nature of the bonding and the interaction between the atoms are clearly revealed by the maps. The bonding in these systems is shown two-dimensionally on the (100) and (110) planes and the one-dimensional electron density profiles along (100), (110) and (111) directions have also been plotted using MEM electron densities. The electron density at the saddle point between the ions has been estimated using these profiles and compared with the available reported results. The resolution of these maps is high and hence these maps can be regarded as the most precise electron density distributions seen inside the chosen materials. The electron content of the doubly ionic oxygen and the cations are estimated from the three-dimensional MEM electron densities by assuming spheres of various radii. The histograms drawn with [FMem(k)−FObs(k)]/σ(k) versus the number of reflections show the validity of the approach and the appropriateness of the Gaussian weighting scheme used in the analysis.