X-RAY STUDY OF THE ELECTRON-DENSITY IN MAGNESITE, MGCO3

The electron density in a naturally faced mineral crystal of MgCO3 was re-measured with Mo Kalpha (lambda = 0.71073 angstrom) diffraction da ta, using extinction corrections that minimize differences between equ ivalent reflection intensities. The deformation electron density has 0 .66 e angstrom-3 density maxima in the C-O bonds and 0.35 e angstrom-3 maxima at the 0-atom lone pairs. Space group R3cBAR, hexagonal, M(r) = 84.31, a 4.635 (1), c = 15.023 (2) angstrom, V = 279.5 (1) angstrom3 , Z = 6, D(x) = 3.005 Mg m-3, mu(Mo Kalpha) = 0.48 mm-1, F(000) = 252, T = 293 K, R = 0.022, wR = 0.025, S = 5.87 for 332 unique reflections .