Deformation Density Study of KMnO4

The electron density distribution of KMnO4 is studied by the X-ray diffraction method. Potassium permanganate crystalizes in an orthorhombic space group Pbnm with cell parameters a=7.3661(7), b=9.0610(9), c=5.6458(3)A, Z=4. The molecular symmetry is CS with the Mn atom and two oxygen atoms located on the plane perpendicular to the c-axis. A set of accurate diffraction data were measured at 115K. Subsequent refinements and Fourier syntheses were performed. The electron density distribution is expressed in terms of the deformation density. The Mn-O bondings are well characterized, the lone pair electron density at the oxygen atoms is also observed. The density near the Mn nucleus seems to be very sensitive to changes of the scale factor and extinction coefficient. Several types of extinction corrections were made. The features of the Mn-O bond are comparable to the theoretical density calculated at the ab-initio level, and to the experimental density of the isoelectronic compound K2CrO4. However, the experimental density of KMnO4 is not so well reproduced in the vicinity of Mn nucleus.