  We demonstrate with LSDA+U calculations that x-ray scattering at the K edge
of Mn is sensitive to orbital ordering in one energy range and Jahn-Teller
distortion in another. Contrary to what is suggested by atomic or cluster
models used to date we show that band structure effects rather than local
Coulomb interactions dominate the polarization dependence of the K edge
scattering and therefore it is sensitive to nearest neighbour bond length
distortions and next nearest neighbour orbital occupation. Based on this we
propose a new mechanism for K edge x-ray scattering in the manganates which we
suggest is also applicable to transition metal compounds in general.
