A SYNCHROTRON X-RAY STUDY OF THE ELECTRON-DENSITY IN YFEO3

Structure factors for synthetic yttrium orthoferrite, YFeO3, measured with MoK alpha (lambda = 0.71073 Angstrom) X-radiation and using a sma ller crystal with focused lambda = 0.75 Angstrom synchrotron radiation are broadly consistent. Approximate symmetry in concordant difference densities indicates that cations deform the electron density more str ongly than O atoms, although the deformation-density (Delta rho) map s ymmetry is lower than that expected from Fe cation interactions alone. The map's local symmetry is influenced strongly by the Y cations, but not by neighbouring O anions. Space group Pnma, orthorhombic, M(r) = 192.76, a = 5.5877(3), b = 7.5951 (4), c = 5.2743 (2) Angstrom, V = 22 3.84 (2) Angstrom(3), Z = 4, D-x = 5.719 Mg m(-3), mu(0.75) = 29.82 mm (-1), F(000) = 356, T = 293 K, R = 0.026, wR = 0.028, S = 5.4 (1) for the 1039 unique reflections of the synchrotron data set.