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Structure of chromium trioxide

F. Hanic and D. Stempelová

Komensky University, Bratislava

Abstract: Bystr.ovrddot.om and Wilhelmi method (CA 45, 3679i), was used. The structure of CrO₃ was detd. with (F_hk0)² and (F_hkl)² analyses and from the projections of electron ds. ρ(x,y) and ρ(y,z). Coeffs. F_0kl were calcd. on the unequalities. The tetrahedral arrangement of 'end' atoms around Cr is deformed by the inclinations of O_III and O_IV from the symmetry level in the opposite directions. With this inclination the bond angle O_III-Cr-O_IV and the interat. distance of 'end' O_III-O_IV is increased. The distance of Cr from the 'end' O atoms is 0.2 A. shorter than the distance of Cr from the O atoms bound into the chain. From the interat. distances and from the differences in the length of Cr-O bonds between Cr and 'bond' O on 1 side, and between Cr and 'end' O on the other side a covalent character for CrO₄ tetrahdra is inferred. The structure of CrO₃ can be expressed as a linear chain of alternating Cr and O atoms with 2 O atoms attached to the sides of each Cr atom. The reliance factor is 0.18 for the projection (001) and 0.22 for the projection (100).

Full paper in Portable Document Format: 143a165.pdf (in Slovak)

Chemical Papers 14 (3) 165–176 (1960)