J. HAUCK 237 smaller interaction. For alloys with small M content such as A 5 M the interaction seems to be too small for a formation of ordered alloys with cubic close packing because of the entropy at elevated temperatures, where A and M are mobile. (1969a). Z. Naturforsch. Teil B, 24, 251. (1969b). Z. Naturforsch. Teil B, 24, 455--456. (1969c). Z. Naturforsch. Teil B, 24, 1064Teil B, 24, -1066Teil B, 24, . ( 1970a. Z. Naturforsch. Teil B, 25, 226. (1970b). Z. Naturforsch. Teil B, 25, 109-110. (1970c). Z. Naturforsch. Teil B, 25, 749-752. (1970d). Z. Naturforsch. TeiI B, 25, 468-471. (1973). Z. Naturforsch. Teil B, 28, 215-216. (1974). J. Inorg. Nucl. Chem. 36, 2291-2298. HAUCK, J. (1976a. Z. Naturforsch. TeilB, 31, 1179-1182. HAUCK, J. (1976b structure is polarized as a result of the symmetries of molecular orbitals in this strongly anisotropic molecule. The extended X-ray absorption fine structure is polarized because of the difference in distance to the axial and equatorial oxygen neighbors. In this wavelength region, the anomalous-scattering terms and © 1980 International Union of Crystallography 238 DOUBLE REFRACTION IN VANADYL BISACETYLACETONATE the index of refraction vary with the direction of polarization. Some of the consequences and possible applications of these properties are discussed.