ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
X-ray structure factors of MgF2 were derived from accurate measurement of single-crystal diffraction intensities. The crystal charge density was analyzed in terms of multipole expansions centered at the ionic sites. Separation of electronic and dynamic deformations was effected by using, in the difference series calculations, anisotropic Debye-Waller factors obtained in the neutron diffraction study of Vidal- Valat, Vidal, Zeyen & Kurki-Suonio [Acta Cryst. (1979), B35, 1584-1590]. The charge density was found to be composed of well defined local Mg2+ ions and slightly enlarged and more diffuse F- ions with 0.50 electrons distributed more widely in the unit cell. Nonspherical deformations of electronic origin were found significant up to fourth order, with the exception of the vanishing dipole moment of fluorine. These deformations emphasize the ionic nature of the crystal by violating the symmetry of the immediate surroundings and by decreasing the charge density in all of the octahedral bonding directions of Mg2+ down to typical ionic values.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0567739481001824
