Electron charge density study on the bonding nature in MoO3

The accurate electron charge density distributions of MoO3 have been investigated by analyzing the synchrotron radiation X-ray powder diffraction data using the MEM (Maximum Entropy Method)/Rietveld method. The covalent bonding is observed only on the five Mo-O bonds, while six O atoms surround the Mo atom. Turning attention to the covalent bonding network, the crystal structure of MoO3 is regarded as a two-dimensional mono-layer structure consisting of the distorted Mo-O-5 pyramids. The ionic state of the Mo atom is estimated to be +3.0(1) and those of three O atoms are -1.6(1), -0.7(1), -0.8(1) by counting number of electrons around these atoms, which coincide with the results of theoretical studies.