Determination of the crystallographic structure of the new U6Fe5Al8Si9 compound

The crystal structure of a new quaternary U6Fe5Al8Si9 orthorhombic compound described by Immm space group was solved and refined on the basis of X-ray powder diffraction data. The unit cell parameters (a = 12.2407(2) إ, b = 18.3614(3) إ, c = 4.0662(1) إ) and the atomic coordinates were optimized through Rietveld refinement procedure with the reliability factors Rp = 8.1%, Rb = 6.2% and Rwp = 11.4%. Density Functional Theory calculations were used to distinguish between positions of Si and Al atoms in the final model of the structure. The positions of heavy atoms observed in high-resolution TEM-images fit their positions on the respective projections of the proposed structural model.